Clean Code concepts adapted for PHP

Related tags

Miscellaneous clean-code-php
Overview

Clean Code PHP

Table of Contents

  1. Introduction
  2. Variables
  3. Comparison
  4. Functions
  5. Objects and Data Structures
  6. Classes
  7. SOLID
  8. Don’t repeat yourself (DRY)
  9. Translations

Introduction

Software engineering principles, from Robert C. Martin's book Clean Code, adapted for PHP. This is not a style guide. It's a guide to producing readable, reusable, and refactorable software in PHP.

Not every principle herein has to be strictly followed, and even fewer will be universally agreed upon. These are guidelines and nothing more, but they are ones codified over many years of collective experience by the authors of Clean Code.

Inspired from clean-code-javascript.

Although many developers still use PHP 5, most of the examples in this article only work with PHP 7.1+.

Variables

Use meaningful and pronounceable variable names

Bad:

$ymdstr = $moment->format('y-m-d');

Good:

$currentDate = $moment->format('y-m-d');

⬆ back to top

Use the same vocabulary for the same type of variable

Bad:

getUserInfo();
getUserData();
getUserRecord();
getUserProfile();

Good:

getUser();

⬆ back to top

Use searchable names (part 1)

We will read more code than we will ever write. It's important that the code we do write is readable and searchable. By not naming variables that end up being meaningful for understanding our program, we hurt our readers. Make your names searchable.

Bad:

// What the heck is 448 for?
$result = $serializer->serialize($data, 448);

Good:

$json = $serializer->serialize($data, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);

Use searchable names (part 2)

Bad:

class User
{
    // What the heck is 7 for?
    public $access = 7;
}

// What the heck is 4 for?
if ($user->access & 4) {
    // ...
}

// What's going on here?
$user->access ^= 2;

Good:

class User
{
    public const ACCESS_READ = 1;

    public const ACCESS_CREATE = 2;

    public const ACCESS_UPDATE = 4;

    public const ACCESS_DELETE = 8;

    // User as default can read, create and update something
    public $access = self::ACCESS_READ | self::ACCESS_CREATE | self::ACCESS_UPDATE;
}

if ($user->access & User::ACCESS_UPDATE) {
    // do edit ...
}

// Deny access rights to create something
$user->access ^= User::ACCESS_CREATE;

⬆ back to top

Use explanatory variables

Bad:

$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
preg_match($cityZipCodeRegex, $address, $matches);

saveCityZipCode($matches[1], $matches[2]);

Not bad:

It's better, but we are still heavily dependent on regex.

$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
preg_match($cityZipCodeRegex, $address, $matches);

[, $city, $zipCode] = $matches;
saveCityZipCode($city, $zipCode);

Good:

Decrease dependence on regex by naming subpatterns.

$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(?
   
    .+?)\s*(?
    
     \d{5})$/'
    
   ;
preg_match($cityZipCodeRegex, $address, $matches);

saveCityZipCode($matches['city'], $matches['zipCode']);

⬆ back to top

Avoid nesting too deeply and return early (part 1)

Too many if-else statements can make your code hard to follow. Explicit is better than implicit.

Bad:

function isShopOpen($day): bool
{
    if ($day) {
        if (is_string($day)) {
            $day = strtolower($day);
            if ($day === 'friday') {
                return true;
            } elseif ($day === 'saturday') {
                return true;
            } elseif ($day === 'sunday') {
                return true;
            }
            return false;
        }
        return false;
    }
    return false;
}

Good:

function isShopOpen(string $day): bool
{
    if (empty($day)) {
        return false;
    }

    $openingDays = ['friday', 'saturday', 'sunday'];

    return in_array(strtolower($day), $openingDays, true);
}

⬆ back to top

Avoid nesting too deeply and return early (part 2)

Bad:

function fibonacci(int $n)
{
    if ($n < 50) {
        if ($n !== 0) {
            if ($n !== 1) {
                return fibonacci($n - 1) + fibonacci($n - 2);
            }
            return 1;
        }
        return 0;
    }
    return 'Not supported';
}

Good:

function fibonacci(int $n): int
{
    if ($n === 0 || $n === 1) {
        return $n;
    }

    if ($n >= 50) {
        throw new Exception('Not supported');
    }

    return fibonacci($n - 1) + fibonacci($n - 2);
}

⬆ back to top

Avoid Mental Mapping

Don’t force the reader of your code to translate what the variable means. Explicit is better than implicit.

Bad:

$l = ['Austin', 'New York', 'San Francisco'];

for ($i = 0; $i < count($l); $i++) {
    $li = $l[$i];
    doStuff();
    doSomeOtherStuff();
    // ...
    // ...
    // ...
    // Wait, what is `$li` for again?
    dispatch($li);
}

Good:

$locations = ['Austin', 'New York', 'San Francisco'];

foreach ($locations as $location) {
    doStuff();
    doSomeOtherStuff();
    // ...
    // ...
    // ...
    dispatch($location);
}

⬆ back to top

Don't add unneeded context

If your class/object name tells you something, don't repeat that in your variable name.

Bad:

class Car
{
    public $carMake;

    public $carModel;

    public $carColor;

    //...
}

Good:

class Car
{
    public $make;

    public $model;

    public $color;

    //...
}

⬆ back to top

Comparison

Use identical comparison

Not good:

The simple comparison will convert the string in an integer.

$a = '42';
$b = 42;

if ($a != $b) {
    // The expression will always pass
}

The comparison $a != $b returns FALSE but in fact it's TRUE! The string 42 is different than the integer 42.

Good:

The identical comparison will compare type and value.

$a = '42';
$b = 42;

if ($a !== $b) {
    // The expression is verified
}

The comparison $a !== $b returns TRUE.

⬆ back to top

Null coalescing operator

Null coalescing is a new operator introduced in PHP 7. The null coalescing operator ?? has been added as syntactic sugar for the common case of needing to use a ternary in conjunction with isset(). It returns its first operand if it exists and is not null; otherwise it returns its second operand.

Bad:

if (isset($_GET['name'])) {
    $name = $_GET['name'];
} elseif (isset($_POST['name'])) {
    $name = $_POST['name'];
} else {
    $name = 'nobody';
}

Good:

$name = $_GET['name'] ?? $_POST['name'] ?? 'nobody';

⬆ back to top

Functions

Use default arguments instead of short circuiting or conditionals

Not good:

This is not good because $breweryName can be NULL.

function createMicrobrewery($breweryName = 'Hipster Brew Co.'): void
{
    // ...
}

Not bad:

This opinion is more understandable than the previous version, but it better controls the value of the variable.

function createMicrobrewery($name = null): void
{
    $breweryName = $name ?: 'Hipster Brew Co.';
    // ...
}

Good:

You can use type hinting and be sure that the $breweryName will not be NULL.

function createMicrobrewery(string $breweryName = 'Hipster Brew Co.'): void
{
    // ...
}

⬆ back to top

Function arguments (2 or fewer ideally)

Limiting the amount of function parameters is incredibly important because it makes testing your function easier. Having more than three leads to a combinatorial explosion where you have to test tons of different cases with each separate argument.

Zero arguments is the ideal case. One or two arguments is ok, and three should be avoided. Anything more than that should be consolidated. Usually, if you have more than two arguments then your function is trying to do too much. In cases where it's not, most of the time a higher-level object will suffice as an argument.

Bad:

class Questionnaire
{
    public function __construct(
        string $firstname,
        string $lastname,
        string $patronymic,
        string $region,
        string $district,
        string $city,
        string $phone,
        string $email
    ) {
        // ...
    }
}

Good:

class Name
{
    private $firstname;

    private $lastname;

    private $patronymic;

    public function __construct(string $firstname, string $lastname, string $patronymic)
    {
        $this->firstname = $firstname;
        $this->lastname = $lastname;
        $this->patronymic = $patronymic;
    }

    // getters ...
}

class City
{
    private $region;

    private $district;

    private $city;

    public function __construct(string $region, string $district, string $city)
    {
        $this->region = $region;
        $this->district = $district;
        $this->city = $city;
    }

    // getters ...
}

class Contact
{
    private $phone;

    private $email;

    public function __construct(string $phone, string $email)
    {
        $this->phone = $phone;
        $this->email = $email;
    }

    // getters ...
}

class Questionnaire
{
    public function __construct(Name $name, City $city, Contact $contact)
    {
        // ...
    }
}

⬆ back to top

Function names should say what they do

Bad:

class Email
{
    //...

    public function handle(): void
    {
        mail($this->to, $this->subject, $this->body);
    }
}

$message = new Email(...);
// What is this? A handle for the message? Are we writing to a file now?
$message->handle();

Good:

class Email
{
    //...

    public function send(): void
    {
        mail($this->to, $this->subject, $this->body);
    }
}

$message = new Email(...);
// Clear and obvious
$message->send();

⬆ back to top

Functions should only be one level of abstraction

When you have more than one level of abstraction your function is usually doing too much. Splitting up functions leads to reusability and easier testing.

Bad:

function parseBetterPHPAlternative(string $code): void
{
    $regexes = [
        // ...
    ];

    $statements = explode(' ', $code);
    $tokens = [];
    foreach ($regexes as $regex) {
        foreach ($statements as $statement) {
            // ...
        }
    }

    $ast = [];
    foreach ($tokens as $token) {
        // lex...
    }

    foreach ($ast as $node) {
        // parse...
    }
}

Bad too:

We have carried out some of the functionality, but the parseBetterPHPAlternative() function is still very complex and not testable.

function tokenize(string $code): array
{
    $regexes = [
        // ...
    ];

    $statements = explode(' ', $code);
    $tokens = [];
    foreach ($regexes as $regex) {
        foreach ($statements as $statement) {
            $tokens[] = /* ... */;
        }
    }

    return $tokens;
}

function lexer(array $tokens): array
{
    $ast = [];
    foreach ($tokens as $token) {
        $ast[] = /* ... */;
    }

    return $ast;
}

function parseBetterPHPAlternative(string $code): void
{
    $tokens = tokenize($code);
    $ast = lexer($tokens);
    foreach ($ast as $node) {
        // parse...
    }
}

Good:

The best solution is move out the dependencies of parseBetterPHPAlternative() function.

class Tokenizer
{
    public function tokenize(string $code): array
    {
        $regexes = [
            // ...
        ];

        $statements = explode(' ', $code);
        $tokens = [];
        foreach ($regexes as $regex) {
            foreach ($statements as $statement) {
                $tokens[] = /* ... */;
            }
        }

        return $tokens;
    }
}

class Lexer
{
    public function lexify(array $tokens): array
    {
        $ast = [];
        foreach ($tokens as $token) {
            $ast[] = /* ... */;
        }

        return $ast;
    }
}

class BetterPHPAlternative
{
    private $tokenizer;
    private $lexer;

    public function __construct(Tokenizer $tokenizer, Lexer $lexer)
    {
        $this->tokenizer = $tokenizer;
        $this->lexer = $lexer;
    }

    public function parse(string $code): void
    {
        $tokens = $this->tokenizer->tokenize($code);
        $ast = $this->lexer->lexify($tokens);
        foreach ($ast as $node) {
            // parse...
        }
    }
}

⬆ back to top

Don't use flags as function parameters

Flags tell your user that this function does more than one thing. Functions should do one thing. Split out your functions if they are following different code paths based on a boolean.

Bad:

function createFile(string $name, bool $temp = false): void
{
    if ($temp) {
        touch('./temp/' . $name);
    } else {
        touch($name);
    }
}

Good:

function createFile(string $name): void
{
    touch($name);
}

function createTempFile(string $name): void
{
    touch('./temp/' . $name);
}

⬆ back to top

Avoid Side Effects

A function produces a side effect if it does anything other than take a value in and return another value or values. A side effect could be writing to a file, modifying some global variable, or accidentally wiring all your money to a stranger.

Now, you do need to have side effects in a program on occasion. Like the previous example, you might need to write to a file. What you want to do is to centralize where you are doing this. Don't have several functions and classes that write to a particular file. Have one service that does it. One and only one.

The main point is to avoid common pitfalls like sharing state between objects without any structure, using mutable data types that can be written to by anything, and not centralizing where your side effects occur. If you can do this, you will be happier than the vast majority of other programmers.

Bad:

// Global variable referenced by following function.
// If we had another function that used this name, now it'd be an array and it could break it.
$name = 'Ryan McDermott';

function splitIntoFirstAndLastName(): void
{
    global $name;

    $name = explode(' ', $name);
}

splitIntoFirstAndLastName();

var_dump($name);
// ['Ryan', 'McDermott'];

Good:

function splitIntoFirstAndLastName(string $name): array
{
    return explode(' ', $name);
}

$name = 'Ryan McDermott';
$newName = splitIntoFirstAndLastName($name);

var_dump($name);
// 'Ryan McDermott';

var_dump($newName);
// ['Ryan', 'McDermott'];

⬆ back to top

Don't write to global functions

Polluting globals is a bad practice in many languages because you could clash with another library and the user of your API would be none-the-wiser until they get an exception in production. Let's think about an example: what if you wanted to have configuration array? You could write global function like config(), but it could clash with another library that tried to do the same thing.

Bad:

function config(): array
{
    return [
        'foo' => 'bar',
    ];
}

Good:

class Configuration
{
    private $configuration = [];

    public function __construct(array $configuration)
    {
        $this->configuration = $configuration;
    }

    public function get(string $key): ?string
    {
        // null coalescing operator
        return $this->configuration[$key] ?? null;
    }
}

Load configuration and create instance of Configuration class

$configuration = new Configuration([
    'foo' => 'bar',
]);

And now you must use instance of Configuration in your application.

⬆ back to top

Don't use a Singleton pattern

Singleton is an anti-pattern. Paraphrased from Brian Button:

  1. They are generally used as a global instance, why is that so bad? Because you hide the dependencies of your application in your code, instead of exposing them through the interfaces. Making something global to avoid passing it around is a code smell.
  2. They violate the single responsibility principle: by virtue of the fact that they control their own creation and lifecycle.
  3. They inherently cause code to be tightly coupled. This makes faking them out under test rather difficult in many cases.
  4. They carry state around for the lifetime of the application. Another hit to testing since you can end up with a situation where tests need to be ordered which is a big no for unit tests. Why? Because each unit test should be independent from the other.

There is also very good thoughts by Misko Hevery about the root of problem.

Bad:

class DBConnection
{
    private static $instance;

    private function __construct(string $dsn)
    {
        // ...
    }

    public static function getInstance(): self
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }

        return self::$instance;
    }

    // ...
}

$singleton = DBConnection::getInstance();

Good:

class DBConnection
{
    public function __construct(string $dsn)
    {
        // ...
    }

    // ...
}

Create instance of DBConnection class and configure it with DSN.

$connection = new DBConnection($dsn);

And now you must use instance of DBConnection in your application.

⬆ back to top

Encapsulate conditionals

Bad:

if ($article->state === 'published') {
    // ...
}

Good:

if ($article->isPublished()) {
    // ...
}

⬆ back to top

Avoid negative conditionals

Bad:

function isDOMNodeNotPresent(DOMNode $node): bool
{
    // ...
}

if (! isDOMNodeNotPresent($node)) {
    // ...
}

Good:

function isDOMNodePresent(DOMNode $node): bool
{
    // ...
}

if (isDOMNodePresent($node)) {
    // ...
}

⬆ back to top

Avoid conditionals

This seems like an impossible task. Upon first hearing this, most people say, "how am I supposed to do anything without an if statement?" The answer is that you can use polymorphism to achieve the same task in many cases. The second question is usually, "well that's great but why would I want to do that?" The answer is a previous clean code concept we learned: a function should only do one thing. When you have classes and functions that have if statements, you are telling your user that your function does more than one thing. Remember, just do one thing.

Bad:

class Airplane
{
    // ...

    public function getCruisingAltitude(): int
    {
        switch ($this->type) {
            case '777':
                return $this->getMaxAltitude() - $this->getPassengerCount();
            case 'Air Force One':
                return $this->getMaxAltitude();
            case 'Cessna':
                return $this->getMaxAltitude() - $this->getFuelExpenditure();
        }
    }
}

Good:

interface Airplane
{
    // ...

    public function getCruisingAltitude(): int;
}

class Boeing777 implements Airplane
{
    // ...

    public function getCruisingAltitude(): int
    {
        return $this->getMaxAltitude() - $this->getPassengerCount();
    }
}

class AirForceOne implements Airplane
{
    // ...

    public function getCruisingAltitude(): int
    {
        return $this->getMaxAltitude();
    }
}

class Cessna implements Airplane
{
    // ...

    public function getCruisingAltitude(): int
    {
        return $this->getMaxAltitude() - $this->getFuelExpenditure();
    }
}

⬆ back to top

Avoid type-checking (part 1)

PHP is untyped, which means your functions can take any type of argument. Sometimes you are bitten by this freedom and it becomes tempting to do type-checking in your functions. There are many ways to avoid having to do this. The first thing to consider is consistent APIs.

Bad:

function travelToTexas($vehicle): void
{
    if ($vehicle instanceof Bicycle) {
        $vehicle->pedalTo(new Location('texas'));
    } elseif ($vehicle instanceof Car) {
        $vehicle->driveTo(new Location('texas'));
    }
}

Good:

function travelToTexas(Vehicle $vehicle): void
{
    $vehicle->travelTo(new Location('texas'));
}

⬆ back to top

Avoid type-checking (part 2)

If you are working with basic primitive values like strings, integers, and arrays, and you use PHP 7+ and you can't use polymorphism but you still feel the need to type-check, you should consider type declaration or strict mode. It provides you with static typing on top of standard PHP syntax. The problem with manually type-checking is that doing it will require so much extra verbiage that the faux "type-safety" you get doesn't make up for the lost readability. Keep your PHP clean, write good tests, and have good code reviews. Otherwise, do all of that but with PHP strict type declaration or strict mode.

Bad:

function combine($val1, $val2): int
{
    if (! is_numeric($val1) || ! is_numeric($val2)) {
        throw new Exception('Must be of type Number');
    }

    return $val1 + $val2;
}

Good:

function combine(int $val1, int $val2): int
{
    return $val1 + $val2;
}

⬆ back to top

Remove dead code

Dead code is just as bad as duplicate code. There's no reason to keep it in your codebase. If it's not being called, get rid of it! It will still be safe in your version history if you still need it.

Bad:

function oldRequestModule(string $url): void
{
    // ...
}

function newRequestModule(string $url): void
{
    // ...
}

$request = newRequestModule($requestUrl);
inventoryTracker('apples', $request, 'www.inventory-awesome.io');

Good:

function requestModule(string $url): void
{
    // ...
}

$request = requestModule($requestUrl);
inventoryTracker('apples', $request, 'www.inventory-awesome.io');

⬆ back to top

Objects and Data Structures

Use object encapsulation

In PHP you can set public, protected and private keywords for methods. Using it, you can control properties modification on an object.

  • When you want to do more beyond getting an object property, you don't have to look up and change every accessor in your codebase.
  • Makes adding validation simple when doing a set.
  • Encapsulates the internal representation.
  • Easy to add logging and error handling when getting and setting.
  • Inheriting this class, you can override default functionality.
  • You can lazy load your object's properties, let's say getting it from a server.

Additionally, this is part of Open/Closed principle.

Bad:

class BankAccount
{
    public $balance = 1000;
}

$bankAccount = new BankAccount();

// Buy shoes...
$bankAccount->balance -= 100;

Good:

class BankAccount
{
    private $balance;

    public function __construct(int $balance = 1000)
    {
      $this->balance = $balance;
    }

    public function withdraw(int $amount): void
    {
        if ($amount > $this->balance) {
            throw new \Exception('Amount greater than available balance.');
        }

        $this->balance -= $amount;
    }

    public function deposit(int $amount): void
    {
        $this->balance += $amount;
    }

    public function getBalance(): int
    {
        return $this->balance;
    }
}

$bankAccount = new BankAccount();

// Buy shoes...
$bankAccount->withdraw($shoesPrice);

// Get balance
$balance = $bankAccount->getBalance();

⬆ back to top

Make objects have private/protected members

  • public methods and properties are most dangerous for changes, because some outside code may easily rely on them and you can't control what code relies on them. Modifications in class are dangerous for all users of class.
  • protected modifier are as dangerous as public, because they are available in scope of any child class. This effectively means that difference between public and protected is only in access mechanism, but encapsulation guarantee remains the same. Modifications in class are dangerous for all descendant classes.
  • private modifier guarantees that code is dangerous to modify only in boundaries of single class (you are safe for modifications and you won't have Jenga effect).

Therefore, use private by default and public/protected when you need to provide access for external classes.

For more information you can read the blog post on this topic written by Fabien Potencier.

Bad:

class Employee
{
    public $name;

    public function __construct(string $name)
    {
        $this->name = $name;
    }
}

$employee = new Employee('John Doe');
// Employee name: John Doe
echo 'Employee name: ' . $employee->name;

Good:

class Employee
{
    private $name;

    public function __construct(string $name)
    {
        $this->name = $name;
    }

    public function getName(): string
    {
        return $this->name;
    }
}

$employee = new Employee('John Doe');
// Employee name: John Doe
echo 'Employee name: ' . $employee->getName();

⬆ back to top

Classes

Prefer composition over inheritance

As stated famously in Design Patterns by the Gang of Four, you should prefer composition over inheritance where you can. There are lots of good reasons to use inheritance and lots of good reasons to use composition. The main point for this maxim is that if your mind instinctively goes for inheritance, try to think if composition could model your problem better. In some cases it can.

You might be wondering then, "when should I use inheritance?" It depends on your problem at hand, but this is a decent list of when inheritance makes more sense than composition:

  1. Your inheritance represents an "is-a" relationship and not a "has-a" relationship (Human->Animal vs. User->UserDetails).
  2. You can reuse code from the base classes (Humans can move like all animals).
  3. You want to make global changes to derived classes by changing a base class. (Change the caloric expenditure of all animals when they move).

Bad:

ssn = $ssn; $this->salary = $salary; } // ... } "> 
class Employee
{
    private $name;

    private $email;

    public function __construct(string $name, string $email)
    {
        $this->name = $name;
        $this->email = $email;
    }

    // ...
}

// Bad because Employees "have" tax data.
// EmployeeTaxData is not a type of Employee

class EmployeeTaxData extends Employee
{
    private $ssn;

    private $salary;

    public function __construct(string $name, string $email, string $ssn, string $salary)
    {
        parent::__construct($name, $email);

        $this->ssn = $ssn;
        $this->salary = $salary;
    }

    // ...
}

Good:

class EmployeeTaxData
{
    private $ssn;

    private $salary;

    public function __construct(string $ssn, string $salary)
    {
        $this->ssn = $ssn;
        $this->salary = $salary;
    }

    // ...
}

class Employee
{
    private $name;

    private $email;

    private $taxData;

    public function __construct(string $name, string $email)
    {
        $this->name = $name;
        $this->email = $email;
    }

    public function setTaxData(EmployeeTaxData $taxData): void
    {
        $this->taxData = $taxData;
    }

    // ...
}

⬆ back to top

Avoid fluent interfaces

A Fluent interface is an object oriented API that aims to improve the readability of the source code by using Method chaining.

While there can be some contexts, frequently builder objects, where this pattern reduces the verbosity of the code (for example the PHPUnit Mock Builder or the Doctrine Query Builder), more often it comes at some costs:

  1. Breaks Encapsulation.
  2. Breaks Decorators.
  3. Is harder to mock in a test suite.
  4. Makes diffs of commits harder to read.

For more information you can read the full blog post on this topic written by Marco Pivetta.

Bad:

class Car
{
    private $make = 'Honda';

    private $model = 'Accord';

    private $color = 'white';

    public function setMake(string $make): self
    {
        $this->make = $make;

        // NOTE: Returning this for chaining
        return $this;
    }

    public function setModel(string $model): self
    {
        $this->model = $model;

        // NOTE: Returning this for chaining
        return $this;
    }

    public function setColor(string $color): self
    {
        $this->color = $color;

        // NOTE: Returning this for chaining
        return $this;
    }

    public function dump(): void
    {
        var_dump($this->make, $this->model, $this->color);
    }
}

$car = (new Car())
    ->setColor('pink')
    ->setMake('Ford')
    ->setModel('F-150')
    ->dump();

Good:

class Car
{
    private $make = 'Honda';

    private $model = 'Accord';

    private $color = 'white';

    public function setMake(string $make): void
    {
        $this->make = $make;
    }

    public function setModel(string $model): void
    {
        $this->model = $model;
    }

    public function setColor(string $color): void
    {
        $this->color = $color;
    }

    public function dump(): void
    {
        var_dump($this->make, $this->model, $this->color);
    }
}

$car = new Car();
$car->setColor('pink');
$car->setMake('Ford');
$car->setModel('F-150');
$car->dump();

⬆ back to top

Prefer final classes

The final keyword should be used whenever possible:

  1. It prevents an uncontrolled inheritance chain.
  2. It encourages composition.
  3. It encourages the Single Responsibility Pattern.
  4. It encourages developers to use your public methods instead of extending the class to get access to protected ones.
  5. It allows you to change your code without breaking applications that use your class.

The only condition is that your class should implement an interface and no other public methods are defined.

For more informations you can read the blog post on this topic written by Marco Pivetta (Ocramius).

Bad:

final class Car
{
    private $color;

    public function __construct($color)
    {
        $this->color = $color;
    }

    /**
     * @return string The color of the vehicle
     */
    public function getColor()
    {
        return $this->color;
    }
}

Good:

interface Vehicle
{
    /**
     * @return string The color of the vehicle
     */
    public function getColor();
}

final class Car implements Vehicle
{
    private $color;

    public function __construct($color)
    {
        $this->color = $color;
    }

    public function getColor()
    {
        return $this->color;
    }
}

⬆ back to top

SOLID

SOLID is the mnemonic acronym introduced by Michael Feathers for the first five principles named by Robert Martin, which meant five basic principles of object-oriented programming and design.

Single Responsibility Principle (SRP)

As stated in Clean Code, "There should never be more than one reason for a class to change". It's tempting to jam-pack a class with a lot of functionality, like when you can only take one suitcase on your flight. The issue with this is that your class won't be conceptually cohesive and it will give it many reasons to change. Minimizing the amount of times you need to change a class is important. It's important because if too much functionality is in one class and you modify a piece of it, it can be difficult to understand how that will affect other dependent modules in your codebase.

Bad:

class UserSettings
{
    private $user;

    public function __construct(User $user)
    {
        $this->user = $user;
    }

    public function changeSettings(array $settings): void
    {
        if ($this->verifyCredentials()) {
            // ...
        }
    }

    private function verifyCredentials(): bool
    {
        // ...
    }
}

Good:

class UserAuth
{
    private $user;

    public function __construct(User $user)
    {
        $this->user = $user;
    }

    public function verifyCredentials(): bool
    {
        // ...
    }
}

class UserSettings
{
    private $user;

    private $auth;

    public function __construct(User $user)
    {
        $this->user = $user;
        $this->auth = new UserAuth($user);
    }

    public function changeSettings(array $settings): void
    {
        if ($this->auth->verifyCredentials()) {
            // ...
        }
    }
}

⬆ back to top

Open/Closed Principle (OCP)

As stated by Bertrand Meyer, "software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification." What does that mean though? This principle basically states that you should allow users to add new functionalities without changing existing code.

Bad:

abstract class Adapter
{
    protected $name;

    public function getName(): string
    {
        return $this->name;
    }
}

class AjaxAdapter extends Adapter
{
    public function __construct()
    {
        parent::__construct();

        $this->name = 'ajaxAdapter';
    }
}

class NodeAdapter extends Adapter
{
    public function __construct()
    {
        parent::__construct();

        $this->name = 'nodeAdapter';
    }
}

class HttpRequester
{
    private $adapter;

    public function __construct(Adapter $adapter)
    {
        $this->adapter = $adapter;
    }

    public function fetch(string $url): Promise
    {
        $adapterName = $this->adapter->getName();

        if ($adapterName === 'ajaxAdapter') {
            return $this->makeAjaxCall($url);
        } elseif ($adapterName === 'httpNodeAdapter') {
            return $this->makeHttpCall($url);
        }
    }

    private function makeAjaxCall(string $url): Promise
    {
        // request and return promise
    }

    private function makeHttpCall(string $url): Promise
    {
        // request and return promise
    }
}

Good:

interface Adapter
{
    public function request(string $url): Promise;
}

class AjaxAdapter implements Adapter
{
    public function request(string $url): Promise
    {
        // request and return promise
    }
}

class NodeAdapter implements Adapter
{
    public function request(string $url): Promise
    {
        // request and return promise
    }
}

class HttpRequester
{
    private $adapter;

    public function __construct(Adapter $adapter)
    {
        $this->adapter = $adapter;
    }

    public function fetch(string $url): Promise
    {
        return $this->adapter->request($url);
    }
}

⬆ back to top

Liskov Substitution Principle (LSP)

This is a scary term for a very simple concept. It's formally defined as "If S is a subtype of T, then objects of type T may be replaced with objects of type S (i.e., objects of type S may substitute objects of type T) without altering any of the desirable properties of that program (correctness, task performed, etc.)." That's an even scarier definition.

The best explanation for this is if you have a parent class and a child class, then the base class and child class can be used interchangeably without getting incorrect results. This might still be confusing, so let's take a look at the classic Square-Rectangle example. Mathematically, a square is a rectangle, but if you model it using the "is-a" relationship via inheritance, you quickly get into trouble.

Bad:

class Rectangle
{
    protected $width = 0;

    protected $height = 0;

    public function setWidth(int $width): void
    {
        $this->width = $width;
    }

    public function setHeight(int $height): void
    {
        $this->height = $height;
    }

    public function getArea(): int
    {
        return $this->width * $this->height;
    }
}

class Square extends Rectangle
{
    public function setWidth(int $width): void
    {
        $this->width = $this->height = $width;
    }

    public function setHeight(int $height): void
    {
        $this->width = $this->height = $height;
    }
}

function printArea(Rectangle $rectangle): void
{
    $rectangle->setWidth(4);
    $rectangle->setHeight(5);

    // BAD: Will return 25 for Square. Should be 20.
    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()) . PHP_EOL;
}

$rectangles = [new Rectangle(), new Square()];

foreach ($rectangles as $rectangle) {
    printArea($rectangle);
}

Good:

The best way is separate the quadrangles and allocation of a more general subtype for both shapes.

Despite the apparent similarity of the square and the rectangle, they are different. A square has much in common with a rhombus, and a rectangle with a parallelogram, but they are not subtypes. A square, a rectangle, a rhombus and a parallelogram are separate shapes with their own properties, albeit similar.

interface Shape
{
    public function getArea(): int;
}

class Rectangle implements Shape
{
    private $width = 0;
    private $height = 0;

    public function __construct(int $width, int $height)
    {
        $this->width = $width;
        $this->height = $height;
    }

    public function getArea(): int
    {
        return $this->width * $this->height;
    }
}

class Square implements Shape
{
    private $length = 0;

    public function __construct(int $length)
    {
        $this->length = $length;
    }

    public function getArea(): int
    {
        return $this->length ** 2;
    }
}

function printArea(Shape $shape): void
{
    echo sprintf('%s has area %d.', get_class($shape), $shape->getArea()).PHP_EOL;
}

$shapes = [new Rectangle(4, 5), new Square(5)];

foreach ($shapes as $shape) {
    printArea($shape);
}

⬆ back to top

Interface Segregation Principle (ISP)

ISP states that "Clients should not be forced to depend upon interfaces that they do not use."

A good example to look at that demonstrates this principle is for classes that require large settings objects. Not requiring clients to set up huge amounts of options is beneficial, because most of the time they won't need all of the settings. Making them optional helps prevent having a "fat interface".

Bad:

interface Employee
{
    public function work(): void;

    public function eat(): void;
}

class HumanEmployee implements Employee
{
    public function work(): void
    {
        // ....working
    }

    public function eat(): void
    {
        // ...... eating in lunch break
    }
}

class RobotEmployee implements Employee
{
    public function work(): void
    {
        //.... working much more
    }

    public function eat(): void
    {
        //.... robot can't eat, but it must implement this method
    }
}

Good:

Not every worker is an employee, but every employee is a worker.

interface Workable
{
    public function work(): void;
}

interface Feedable
{
    public function eat(): void;
}

interface Employee extends Feedable, Workable
{
}

class HumanEmployee implements Employee
{
    public function work(): void
    {
        // ....working
    }

    public function eat(): void
    {
        //.... eating in lunch break
    }
}

// robot can only work
class RobotEmployee implements Workable
{
    public function work(): void
    {
        // ....working
    }
}

⬆ back to top

Dependency Inversion Principle (DIP)

This principle states two essential things:

  1. High-level modules should not depend on low-level modules. Both should depend on abstractions.
  2. Abstractions should not depend upon details. Details should depend on abstractions.

This can be hard to understand at first, but if you've worked with PHP frameworks (like Symfony), you've seen an implementation of this principle in the form of Dependency Injection (DI). While they are not identical concepts, DIP keeps high-level modules from knowing the details of its low-level modules and setting them up. It can accomplish this through DI. A huge benefit of this is that it reduces the coupling between modules. Coupling is a very bad development pattern because it makes your code hard to refactor.

Bad:

class Employee
{
    public function work(): void
    {
        // ....working
    }
}

class Robot extends Employee
{
    public function work(): void
    {
        //.... working much more
    }
}

class Manager
{
    private $employee;

    public function __construct(Employee $employee)
    {
        $this->employee = $employee;
    }

    public function manage(): void
    {
        $this->employee->work();
    }
}

Good:

interface Employee
{
    public function work(): void;
}

class Human implements Employee
{
    public function work(): void
    {
        // ....working
    }
}

class Robot implements Employee
{
    public function work(): void
    {
        //.... working much more
    }
}

class Manager
{
    private $employee;

    public function __construct(Employee $employee)
    {
        $this->employee = $employee;
    }

    public function manage(): void
    {
        $this->employee->work();
    }
}

⬆ back to top

Don’t repeat yourself (DRY)

Try to observe the DRY principle.

Do your absolute best to avoid duplicate code. Duplicate code is bad because it means that there's more than one place to alter something if you need to change some logic.

Imagine if you run a restaurant and you keep track of your inventory: all your tomatoes, onions, garlic, spices, etc. If you have multiple lists that you keep this on, then all have to be updated when you serve a dish with tomatoes in them. If you only have one list, there's only one place to update!

Often you have duplicate code because you have two or more slightly different things, that share a lot in common, but their differences force you to have two or more separate functions that do much of the same things. Removing duplicate code means creating an abstraction that can handle this set of different things with just one function/module/class.

Getting the abstraction right is critical, that's why you should follow the SOLID principles laid out in the Classes section. Bad abstractions can be worse than duplicate code, so be careful! Having said this, if you can make a good abstraction, do it! Don't repeat yourself, otherwise you'll find yourself updating multiple places any time you want to change one thing.

Bad:

function showDeveloperList(array $developers): void
{
    foreach ($developers as $developer) {
        $expectedSalary = $developer->calculateExpectedSalary();
        $experience = $developer->getExperience();
        $githubLink = $developer->getGithubLink();
        $data = [$expectedSalary, $experience, $githubLink];

        render($data);
    }
}

function showManagerList(array $managers): void
{
    foreach ($managers as $manager) {
        $expectedSalary = $manager->calculateExpectedSalary();
        $experience = $manager->getExperience();
        $githubLink = $manager->getGithubLink();
        $data = [$expectedSalary, $experience, $githubLink];

        render($data);
    }
}

Good:

function showList(array $employees): void
{
    foreach ($employees as $employee) {
        $expectedSalary = $employee->calculateExpectedSalary();
        $experience = $employee->getExperience();
        $githubLink = $employee->getGithubLink();
        $data = [$expectedSalary, $experience, $githubLink];

        render($data);
    }
}

Very good:

It is better to use a compact version of the code.

function showList(array $employees): void
{
    foreach ($employees as $employee) {
        render([$employee->calculateExpectedSalary(), $employee->getExperience(), $employee->getGithubLink()]);
    }
}

⬆ back to top

Translations

This is also available in other languages:

⬆ back to top

Comments

  • "Bad" example for "Functions should do one thing" has a bug

    https://github.com/jupeter/clean-code-php#functions-should-do-one-thing

    Notice: Undefined variable: db on line 4

    I can see 3 ways to fix it:

    // OOP: it is a function of an object (a method)
function emailClients($clients) {
    foreach ($clients as $client) {
        $clientRecord = $this->db->find($client);
        if ($clientRecord->isActive()) {
            email($client);
        }
    }
}

    // $db is passed as an argument
function emailClients($clients, $db) {
    foreach ($clients as $client) {
        $clientRecord = $db->find($client);
        if ($clientRecord->isActive()) {
            email($client);
        }
    }
}

    // the function is a closure
$emailClients = function ($clients) use ($db) {
    foreach ($clients as $client) {
        $clientRecord = $db->find($client);
        if ($clientRecord->isActive()) {
            email($client);
        }
    }
};

    See also https://github.com/jupeter/clean-code-php/issues/38

    opened by MacDada 18
  • Translate into other languages

    Translate into other languages

    opened by peter-gribanov 17
  • [Enhancement] Correct use searchable names

    [Enhancement] Correct use searchable names

    Fix for Use searchable names.

    This is bullshit

    // Declare them as capitalized `const` globals.
interface DateGlobal {
    const SECONDS_IN_A_DAY = 86400;
}
 
addExpireAt(DateGlobal::SECONDS_IN_A_DAY);

    You created a global constants. Is not a good. Any class/function can depend on these constants and it will be difficult to put them into a separate component. Your constants is not a informative. Requires each time to create a new constant if you have complex conditions. Example:

    interface DateGlobal {
    const SECONDS_IN_A_HOUR = 3600;
    const SECONDS_IN_A_DAY = 86400;
    const SECONDS_IN_A_WEEK = 604800;
    //const SECONDS_IN_A_MONTH = ???;
    //const SECONDS_IN_A_YEAR = ???;
    const SECONDS_IN_A_TEN_MINUTES = 600;
    const SECONDS_IN_A_FOUR_WEEK = 2419200;
    const SECONDS_IN_A_SOMETHING = 1036800;
    // ...
}

    If you really want to use constants, you must declare them in the context of use.

    class ArticleController
{
    /**
     * By default the response is cached in 3600 seconds (1 hour).
     *
     * @var int
     */
    const DEFAULT_CACHE_TTL = 3600;

    public function showAction(Article $article)
    {
        $ttl = self::DEFAULT_CACHE_TTL;

        // change default TTL in context if need
        // ...

        $response = new Response();
        $response
            ->setMaxAge($ttl)
            ->setSharedMaxAge($ttl)
            ->setExpires(new \DateTime(sprintf('+%d seconds', $ttl)))
        ;

        // ...
    }
}

    There is no misunderstanding.

    enhancement 
    opened by peter-gribanov 15
  • Delete

    Delete "Functions should do one thing" section

    Decided to delete section Functions should do one thing https://github.com/jupeter/clean-code-php/issues/38#issuecomment-532558057

    EDIT by @TomasVotruba : Closes #38

    opened by peter-gribanov 14
  • Add travis checks for spaces and table of contents

    Add travis checks for spaces and table of contents

    Introduce travis build to automatically check:

    • [x] Spaces at the end of lines
    • [x] Table of Contents outdated

    As you can see in the build on my repo, there are issues: https://travis-ci.org/Slamdunk/clean-code-php/builds/274983097

    The maintainer have to activate the travis triggers in repo settings in order for the build to be run on each PR/commit.

    opened by Slamdunk 13
  • Convert method-chaining/fluent-interfaces to be an anti-pattern

    Convert method-chaining/fluent-interfaces to be an anti-pattern

    As correctly said in the chapter Prefer composition over inheritance, composition is an essential design pattern for a good object-oriented clean code.

    Method chaining, also known as Fluent interfaces, breaks composition and in my humble opinion it should be considered an anti-pattern (even though one of the least evil): https://ocramius.github.io/blog/fluent-interfaces-are-evil/

    opened by Slamdunk 12
  • Drop singleton

    Drop singleton

    opened by peter-gribanov 7
  • [ISP] Rename classes to avoid confusion

    [ISP] Rename classes to avoid confusion

    Rename the classes to indicate that these are not entities in a global context. Some people have problems with this.

    In a global context, an employee is a particular case of a human. In the context of employees it will be vice versa. Human is a special case of employees.

    opened by peter-gribanov 6
  • Column size

    Column size

    Quote from Clean Code book:

    "Of course we said that at a time when VT100 screens were 24 lines by 80 columns, and our editors used 4 lines for administrative purposes. Nowadays with a cranked-down font and a nice big monitor, you can fit 150 characters on a line and a 100 lines or more on a screen. Lines should not be 150 characters long. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long."

    More vertical code than horizontal to keep easy to read. :)

    opened by webysther 6
  • Expand description of Singleton

    Expand description of Singleton

    See comment https://github.com/jupeter/clean-code-php/issues/61#issuecomment-327727596 Description from https://stackoverflow.com/a/138012/2455621

    This is not the best description, but it will come off for a start.

    opened by peter-gribanov 5
  • Add and fix a example code

    Add and fix a example code

    It adds an example without the bad or good, on the contrary the same code is shown to notice the difference of a better reading of code.

    The Liskov example replaces the abstract class with an interface for a better understanding of the principle.

    opened by uetiko 5
  • Define constants in those methods where you use, not globally

    Define constants in those methods where you use, not globally

    // Bad

    class MyClass { private const MY_CONSTANT = 5;

    // public function myFunction(): void {

    $myVar = self::MY_CONSTANT;

    }

    // Good idea? Let's check it out!

    class MyClass {

    public function myFunction(): void { $MY_CONSTANT = 5; $myVar = $MY_CONSTANT;

    }

    opened by abelardolg 0
  • add: Indonesian translation section + Refactor code under collapsible markdown

    add: Indonesian translation section + Refactor code under collapsible markdown

    In this PR, I did the following:

    • [x] Grammar errors fixed
    • [x] Adding Indonesian translation repo (mine, still WIP)
    • [x] Adding refactor code optional under collapsible markdown to understand and focus more on which part of the code is bad and good at the end (still WIP)
    opened by ranggakd 1
  • An array is a dumb container of unknown data

    An array is a dumb container of unknown data

    Arrays should be used to store lists: keyless elements of the same type.

    Would you welcome a PR explaining associative arrays should be intelligent objects?

    opened by szepeviktor 0
Owner
Piotr Plenik
Piotr Plenik
GitHub
Clean Code concepts adapted for PHP

PHP Temiz Kod İçindekiler Giriş Değişkenler Anlamlı ve telaffuz edilebilir değişken isimleri kullanın Aynı türden değişkenler için aynı kelimeleri kul

Anıl Özmen 122 Dec 25, 2022
Documentation on clean coding and demonstration of studied clean coding principals with PHP.

practice-php-clean-code Documentation on clean coding and demonstration of studied clean coding principals with PHP. The document contained in this re

Ferdous Islam 1 Feb 21, 2022
My personal tool that I adapted for the company and my colleagues.

xarites-workflow My personal tool that I adapted for the company and my colleagues. XARITES THE CREATIVE AGENCY SRL Automation workflow Created by Vec

Vecsei Szilveszter 2 Nov 17, 2022
YesilCMS is based on BlizzCMS and specifically adapted for VMaNGOS Core and includes new features and many bug fixes.

YesilCMS · YesilCMS is based on BlizzCMS and specifically adapted for VMaNGOS Core and includes new features and many bug fixes. Features In addition

yesilmen 12 Jan 4, 2023
Demonstration of OOP concepts and usage of Abstract class & Interfaces

Learn OOP Demonstration of OOP concepts and usage of Abstract class & Interfaces Usage clone this repo run composer install run php index.php Code str

M N Islam Shihan 3 Sep 14, 2021
A library for adding economic concepts.

PHP use binary version 8.0.10 use PocketMine-MP version API4-beta11+dev2067 Init use oiran\walletlib\api\WalletLib; use oiran\walletlib\api\WarningLev

null 12 Jan 30, 2022
A library for adding economic concepts.

Summary This plugin adds the concept of money to the server. Wallet data held by the player is stored in .json format and I/O asynchronously. As for t

null 12 Jan 30, 2022
Conceptos de Clean Code adaptados para PHP

Clean Code PHP Traducción al español de Clean Code PHP realizado por Jupeter. Si encuentras un error de ortografía, de redacción o de traducción; no d

Francisco Borquez 70 Dec 30, 2022
PHP Simple M3U Parser, it clean the playlist and remove duplicate

SimpleM3UParser PHP Simple M3U Playlist Parser, it clean, remove duplicate, and group the playlist. Usage see example.php <?php require_once "M3UPars

erwin solihin 3 May 30, 2022
A super simple, clean and pretty error handler that replace the default error handler of PHP. You need only include this file!

php-custom-error-handler A super simple, clean and pretty error handler that replace the default error handler of PHP. You need just include only this

null 6 Nov 7, 2022
my personal example of Laravel clean architecture

what is this repo about Clean Architect Laravel ###run we assume docker desktop is up and running open up a terminal cd project directory run "cp .env

Sadegh Salari 37 Dec 23, 2022
A PocketMine-MP plugin that can reduce or clean up the chunks in your world

AutoClearChunk A PocketMine-MP plugin that can reduce or clean up the chunks in your world Features Custom Clear Message Custom Clear Interval Time Pe

HazardTeam 6 Mar 10, 2022
POC d'un projet Clean Architecture + DDD

Proof Of Concept - Clean Architecture & DDD Installation Dans un premier temps, cloner le repository : git clone https://github.com/TBoileau/rse cd rs

Thomas Boileau 11 Sep 3, 2022
A collection of functions to clean up WordPress

Clean WordPress Admin A collection of functions to clean up WordPress front and back-end to make it easier for editors to work and for you to look at

Vincent Orback 411 Dec 28, 2022
A faster drop in replacement for bin/magento cache:clean with file watcher

"You know, hope is a mistake. If you can't fix what's broken, you'll, uh... you'll go insane." - Max Rockatansky Magento 2 Cache Clean A faster drop i

mage2tv 460 Dec 26, 2022
Dockerise Symfony Application (Symfony 6 + Clean Architecture+ DDD+ CQRS + Docker + Xdebug + PHPUnit + Doctrine ORM + JWT Auth + Static analysis)

Symfony Dockerise Symfony Application Install Docker Install Docker Compose Docker PHP & Nginx Create Symfony Application Debugging Install Xdebug Con

null 48 Jan 5, 2023
Clean Architecture, DDD and CQRS using Symfony 6

Task manager system using Clean Architecture, DDD and CQRS. Environment setup Install Docker Clone the project: git clone https://github.com/k0t9i/Tas

null 3 Sep 5, 2022
Test and enforce architectural rules in your Laravel applications. Keep your app's architecture clean and consistent!

Laravel Arkitect Laravel Arkitect lets you test and enforce your architectural rules in your Laravel applications, and it's a PHPArkitect wrapper for

SMorteza Ebadi 55 Dec 17, 2022
Result of our code-along meetup writing PHP 8.1 code

PHP 8.1 Demo Code This code demonstrates various PHP 8.0 and 8.1 features in a realistic, functional (but incomplete) codebase. The code is part of so

azPHP 2 Nov 14, 2021