- مقدمه
- مغیر ها
- از نام های با معنی و قابل تلفظ استفاده کنید
- از واژه یکسان برای همان نوع از متغیر استفاده کنید
- از اسامی قابل جستجو استفاده کنید (بخش اول)
- از اسامی قابل جستجو استفاده کنید (بخش دوم)
- از اسامی توضیحی استفاده کنید
- از تو در تویی زیاد اجتناب کنید و زودتر برگردید (بخش اول)
- از تو در تویی زیاد اجتناب کنید و زودتر برگردید (بخش دوم)
- از نقشه ذهنی کشیدن اجتناب کنید
- مطالب غیر ضروری اضافه نکنید
- مقایسه
- توابع
- از آرگومان های پیشفرض به جای خط های کوتاه یا شرطی استفاده کنید
- آرگومان های توابع (2 یا کمتر به صورت ایده آل)
- نام های نوابع باید بگویند که چکار میکنند
- توابع فقط باید یک سطح از انتزاع را داشته باشند
- از فلگ ها (flags) به عنوان پارامتر فانکشن استفاده نکنید
- از اثرات جانبی اجتناب کنید
- توابع گلوبال (global) را ننویسید
- از الگوی singelton استفاده نکنید
- شرط هارا کپسوله نکنید
- از شرط های منفی اجتناب کنید
- از شرطی شدن اجتناب کنید
- از برسی تایپ ها اجتناب کنید (بخش اول)
- از برسی تایپ ها اجتناب کنید (بخش دوم)
- کد های مرده را حذف کنید
- اشیا (objects) و ساخمان داده
- کلاس ها
- سالید (SOLID)
- خودت رو تکرار نکن (DRY)
- ترجمه ها
اصول مهندسی نرم افزار از کتاب رابرت سی مارتین Clean Code, برای PHP سازگار شده است . این یک راهنمای سبک نیست! بلکه یک راهنمای تولید نرم افزار های قابل خواندن ، قابل استفاده مجدد و قابل بازسازی (refactorable) در php است.
حتما لازم نیست که همه ی اصل های اینجا را رعایت کنید . اینها صرفا راهنما هستند نه بیشتر و حتی تعداد کمی به صورت عمومی خواهد بود اما اینها اصولی هستند که روی آنها تواق شده و در بسیاری از موارد قانون شده اند . سالها تجربه جمعی نویسندگان clean code
الهام گرفته شده از clean-code-javascript.
با اینکه بیشتر توسعه دهندگان php از نسخه .5 استفاده میکنند اما بیشتر مثال های این مقاله با نسخه های بالاتر از 7.1 کار خواهند کرد
بد:
$ymdstr = $moment->format('y-m-d');خوب:
$currentDate = $moment->format('y-m-d');بد:
getUserInfo();
getUserData();
getUserRecord();
getUserProfile();خوب:
getUser();ما بیشتر از آنچه که قراره بخونیم کد مینویسم . این مهمه که کدی مینویسیم قابل خواندن و قابل جستجو باشد . با عدم نام بردن اس متغیر هایی که در اینده برای خوانندگان کد برای درک برنامه معنی دار میشود به خوانندگان صدمه میزنیم
بد:
// What the heck is 448 for?
$result = $serializer->serialize($data, 448);خوب:
$json = $serializer->serialize($data, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);بد:
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;خوب:
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;بد:
$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
preg_match($cityZipCodeRegex, $address, $matches);
saveCityZipCode($matches[1], $matches[2]);بد نیست:** این بهتره، اما هنوز به رجکس بستگی داره
$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
preg_match($cityZipCodeRegex, $address, $matches);
[, $city, $zipCode] = $matches;
saveCityZipCode($city, $zipCode);خوب:
با نام گذاری زیر الگو ها وابستگی به رجکس را کاهش دهید
$address = 'One Infinite Loop, Cupertino 95014';
$cityZipCodeRegex = '/^[^,]+,\s*(?<city>.+?)\s*(?<zipCode>\d{5})$/';
preg_match($cityZipCodeRegex, $address, $matches);
saveCityZipCode($matches['city'], $matches['zipCode']);تعداد زیاد ساختار if-else میتواند کد شما را برای دنبال کردن سخت کند . صریح بهتر از ضمنی است.
بد:
function isShopOpen($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;
}خوب:
function isShopOpen(string $day): bool
{
if (empty($day)) {
return false;
}
$openingDays = ['friday', 'saturday', 'sunday'];
return in_array(strtolower($day), $openingDays, true);
}بد:
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';
}خوب:
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);
}خواننده کدت رو مجبور نکن که معنی متغیر هاتو ترجمه کنه صریح بهتر از ضمنی است
بد:
$l = ['Austin', 'New York', 'San Francisco'];
for ($i = 0; $i < count($l); $i++) {
$li = $l[$i];
doStuff();
doSomeOtherStuff();
// ...
// ...
// ...
// Wait, what is `$li` for again?
dispatch($li);
}خوب:
$locations = ['Austin', 'New York', 'San Francisco'];
foreach ($locations as $location) {
doStuff();
doSomeOtherStuff();
// ...
// ...
// ...
dispatch($location);
}اگر اسم کلاس/شی شما چیزی به شما میگه دیگه اونو تو متغیر ها تکرار نکنید
بد:
class Car
{
public $carMake;
public $carModel;
public $carColor;
//...
}خوب:
class Car
{
public $make;
public $model;
public $color;
//...
}از مقایسه یکسان استفاده کنید
خوب نیست: مقایسه ساده رشته را به عدد تبدیل میکند
$a = '42';
$b = 42;
if ($a != $b) {
// The expression will always pass
}مقایسه‌ی b$ =! $a غلط (False) برمیگردونه اما در واقع درسته (True)
رشته‌ی 42 با عدد 42 متفاوت است
خوب: مقایسه یکسان نوع (type) و مقدار را (value ) را باهم مقایسه میکند
$a = '42';
$b = 42;
if ($a !== $b) {
// The expression is verified
}مقایسه‌ی b$ =! $a درست (True) بر میگردونه
⬆ برگشت به بالا
ادغام کننده null یه عملگر جدیده که توی php 7 معرفی شد عملگر ادغام کننده null ?? به نحوی برای حالت رایج نیاز به یک استفاده از حالت سه تایی ()isset اگه وجود داشته باشه و null نباشه عملوند اول رو برمیگردونه در غیر این صورت عملوند دوم رو بر میگردونه
بد:
if (isset($_GET['name'])) {
$name = $_GET['name'];
} elseif (isset($_POST['name'])) {
$name = $_POST['name'];
} else {
$name = 'nobody';
}خوب:
$name = $_GET['name'] ?? $_POST['name'] ?? 'nobody';خوب نیست:
این خوب نیست چون breweryName$ میتونه Null باشه
function createMicrobrewery($breweryName = 'Hipster Brew Co.'): void
{
// ...
}بد نیست:
این گزینه از قبلی قابل فهم تره اما مقدار متغیر رو بهتر کنترل میکنه
function createMicrobrewery($name = null): void
{
$breweryName = $name ?: 'Hipster Brew Co.';
// ...
}خوب:
شما میتوانید از type hinting استفاده کنید و مطمئن بشید که breweryName$ . نمیتونه NULL بشه
function createMicrobrewery(string $breweryName = 'Hipster Brew Co.'): void
{
// ...
}محدود کردن تعداد پارامتر های یک تابع به طور باور نکردنی ای مهمه چون تست کردن تابع شمارو آسون تر میکنه داشتن بیشتر از 3 تا پارامتر منجر به یک انفجار ترکیبی میشه که شما توی اون باید توی اون موارد مختلف رو با آرگومان های جداگانه ازمایش کنید
گزینه ایده آل صفر تا آرگومانه ، یک یا دو آرگومان اوکی ان و از سه تار آرگومان باید اجتناب کرد. , و هرچیزی بیشتر از این باید [با یکدیگر] تلفیق شود معمولا اگه شما بیشتر از دوتا آرگومان توی تابعتون داشته باشید . تابع شما سعی میکنه تا کار های زیادی انجام بده . توی مواردی اینطوری نیس یک شی (object) سطح بالا به عنوان آرگومان کافیه
بد:
class Questionnaire
{
public function __construct(
string $firstname,
string $lastname,
string $patronymic,
string $region,
string $district,
string $city,
string $phone,
string $email
) {
// ...
}
}خوب:
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 $contact)
{
// ...
}
}بد:
class Email
{
//...
public function handle(): void
{
mail($this->to, $this->subject, $this->body);
}
}
$message = new Email(...);
// What is this? A handle for the message? Are we writing to a file now?
$message->handle();خوب:
class Email
{
//...
public function send(): void
{
mail($this->to, $this->subject, $this->body);
}
}
$message = new Email(...);
// Clear and obvious
$message->send();وقتی شما بیشتر از یک سطح از انتزاع دارید تابع شما معمولا کار زیادی انجام میدهد تقسیم توابع منجر به استفاده مجدد و آسان تر میشود.
تست کردن
بد:
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...
}
}** باز هم بد:**
ما بعضی از کار های functionality (ابع محور بودن) را انجام دادمی اما تابع ()parseBetterPHPAlternative هنوز خیلی پیچیده و غیر قابل تسته.
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...
}
}خوب:
The best solution is move out the dependencies of parseBetterPHPAlternative() function.
بهترین راه حل بیرون کردن وابستگی ها از تابع ()parseBetterPHPAlternative است
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...
}
}
}فلگ ها به کاربر شما میگن که این تابع بیشتر از یک چیزه . تابع باید یک کار انجام بده . اگر توابع شما بر اساس یک بولین (boolean) کارهای متفاوتی میکنند اونارو تقسیم کنید.
بد:
function createFile(string $name, bool $temp = false): void
{
if ($temp) {
touch('./temp/' . $name);
} else {
touch($name);
}
}خوب:
function createFile(string $name): void
{
touch($name);
}
function createTempFile(string $name): void
{
touch('./temp/' . $name);
}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.
اگر یک تابع کاری غیر از گرفتن مقدار و برگردان یک مقدار یا مقدار های دیگر انجام دهد یک اثر جانبی ایجاد می کند یک اثر جانبی می تواند نوشتن در یک فایل، تغییر دادن یک متغیر گلوبال، یا به طور تصادفی تمام پول خود را به یک غریبه متصل کنید.
در حال حاضر، شما نیاز به تاثیرات جانبی در یک برنامه در مواردی دارید. مانند مثال قبلی، ممکن است لازم باشد در یک فایل بنویسید. کاری که می خواهید انجام دهید این است که در جایی که این کار را انجام می دهید متمرکز شوید. چندین توابع و کلاس که در یک فایل خاص بنویسند ندارند. یک سرویس داشته باشید که این کار را انجام دهد. یک و تنها یکی.
نکته اصلی اینه که از تله های رایج مثل اشتراک گذاری حالت(state ) ها بین اشیا (objects) بدون هیچ ساختاری با استفاده از تایپ ها مختلف داده که میتواند به وسیله هر چیزی نوشته شود و محل بروز اثرات جانبی شما را متمرکز نمیکند اجتناب کنید اگه شما بتونید این کار رو بکنید نسب به اکثر برنامه نویس ها شادتر خواهید بود
بد:
// 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'];خوب:
function splitIntoFirstAndLastName(string $name): array
{
return explode(' ', $name);
}
$name = 'Ryan McDermott';
$newName = splitIntoFirstAndLastName($name);
var_dump($name);
// 'Ryan McDermott';
var_dump($newName);
// ['Ryan', 'McDermott'];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.
آلودگی گلوبال ها در بسیاری از زبان‌ها عمل بدی است، زیرا ممکن است با کتابخانه دیگری برخورد کنید و کاربر API شما عاقل‌تر نخواهد بود تا زمانی که در پروداکشن استثناء دریافت نکند. بیایید در باره یک مثال فکر کنیم : اگه شما بخواهید ارایه رو پیکربندی کنی چی؟ بد:
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.
Singleton is an anti-pattern. Paraphrased from Brian Button:
- 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.
- They violate the single responsibility principle: by virtue of the fact that they control their own creation and lifecycle.
- They inherently cause code to be tightly coupled. This makes faking them out under test rather difficult in many cases.
- 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.
Bad:
if ($article->state === 'published') {
// ...
}Good:
if ($article->isPublished()) {
// ...
}Bad:
function isDOMNodeNotPresent(DOMNode $node): bool
{
// ...
}
if (! isDOMNodeNotPresent($node)) {
// ...
}Good:
function isDOMNodePresent(DOMNode $node): bool
{
// ...
}
if (isDOMNodePresent($node)) {
// ...
}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() - $this->getFuelExpenditure();
}
}PHP is untyped, which means your functions can take any type of argument. Sometimes you are bitten by this freedom and it becomes tempting to do type-checking in your functions. There are many ways to avoid having to do this. The first thing to consider is consistent APIs.
Bad:
function travelToTexas($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
{
$vehicle->travelTo(new Location('texas'));
}If you are working with basic primitive values like strings, integers, and arrays, and you use PHP 7+ and you can't use polymorphism but you still feel the need to type-check, you should consider type declaration or strict mode. It provides you with static typing on top of standard PHP syntax. The problem with manually type-checking is that doing it will require so much extra verbiage that the faux "type-safety" you get doesn't make up for the lost readability. Keep your PHP clean, write good tests, and have good code reviews. Otherwise, do all of that but with PHP strict type declaration or strict mode.
Bad:
function combine($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;
}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');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();publicmethods 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.protectedmodifier 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.privatemodifier 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();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:
- Your inheritance represents an "is-a" relationship and not a "has-a" relationship (Human->Animal vs. User->UserDetails).
- You can reuse code from the base classes (Humans can move like all animals).
- 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:
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;
}
// ...
}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:
- Breaks Encapsulation.
- Breaks Decorators.
- Is harder to mock in a test suite.
- 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();The final keyword should be used whenever possible:
- It prevents an uncontrolled inheritance chain.
- It encourages composition.
- It encourages the Single Responsibility Principle.
- It encourages developers to use your public methods instead of extending the class to get access to protected ones.
- 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;
}
}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.
- S: Single Responsibility Principle (SRP)
- O: Open/Closed Principle (OCP)
- L: Liskov Substitution Principle (LSP)
- I: Interface Segregation Principle (ISP)
- D: Dependency Inversion Principle (DIP)
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()) {
// ...
}
}
}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);
}
}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);
}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
}
}This principle states two essential things:
- High-level modules should not depend on low-level modules. Both should depend on abstractions.
- 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();
}
}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()]);
}
}This is also available in other languages:
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