PHP Cheat Sheet
Complete reference guide for PHP with interactive examples and live playground links
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Basic Syntax
Hello World
Different ways to output text in PHP
PHP
<?php
// Basic output
echo "Hello, World!";
print "Hello, World!";
// HTML output
echo "<h1>Hello, World!</h1>";
// String concatenation
$name = "PHP";
echo "Hello, " . $name . "!";
// String interpolation
echo "Hello, $name!";
echo "Hello, {$name}!";
?>Variables and Data Types
Variable declaration and basic data types in PHP
PHP
<?php
// Variable declaration
$name = "PHP";
$age = 30;
$isActive = true;
// Data types
$string = "Hello"; // String
$integer = 42; // Integer
$float = 3.14; // Float
$boolean = true; // Boolean
$null = null; // Null
$array = [1, 2, 3]; // Array
$object = new stdClass(); // Object
// Type checking
var_dump($string); // string(5) "Hello"
is_string($string); // true
is_int($integer); // true
is_bool($boolean); // true
// Type casting
$number = (int) "42";
$string = (string) 42;
$boolean = (bool) 1;String Operations
Common string operations and formatting
PHP
<?php
$text = "Hello World";
// String functions
echo strtoupper($text); // HELLO WORLD
echo strtolower($text); // hello world
echo str_replace("World", "PHP", $text); // Hello PHP
print_r(explode(" ", $text)); // ["Hello", "World"]
echo strlen($text); // 11
// String formatting
$name = "Alice";
$age = 25;
printf("My name is %s and I'm %d years old", $name, $age);
// Heredoc syntax
$html = <<<HTML
<div>
<h1>$name</h1>
<p>Age: $age</p>
</div>
HTML;Arrays
Working with arrays in PHP
PHP
<?php
// Indexed arrays
$fruits = ["apple", "banana", "cherry"];
array_push($fruits, "orange");
array_unshift($fruits, "grape");
array_pop($fruits);
array_shift($fruits);
echo $fruits[0]; // apple
echo count($fruits); // 3
// Associative arrays
$person = [
"name" => "Alice",
"age" => 25,
"job" => "Developer"
];
echo $person["name"]; // Alice
// Array functions
$numbers = [1, 2, 3, 4, 5];
$doubled = array_map(fn($n) => $n * 2, $numbers);
$even = array_filter($numbers, fn($n) => $n % 2 === 0);
$sum = array_reduce($numbers, fn($a, $b) => $a + $b, 0);
// Array destructuring
[$first, $second, ...$rest] = $numbers;Control Structures
Control flow statements in PHP
PHP
<?php
// If-else
if ($age >= 18) {
echo "Adult";
} elseif ($age >= 13) {
echo "Teenager";
} else {
echo "Child";
}
// Switch
switch ($status) {
case "active":
echo "User is active";
break;
case "inactive":
echo "User is inactive";
break;
default:
echo "Unknown status";
}
// Loops
for ($i = 0; $i < 5; $i++) {
echo $i;
}
foreach ($items as $item) {
echo $item;
}
while ($condition) {
// Do something
}
// Match expression (PHP 8.0+)
$result = match($status) {
"active" => "User is active",
"inactive" => "User is inactive",
default => "Unknown status"
};Functions
Function Definition
Different ways to define functions
PHP
<?php
// Basic function
function greet($name) {
return "Hello, $name!";
}
// Function with type hints
function calculate(int $a, int $b): int {
return $a + $b;
}
// Function with default parameters
function createUser($name, $age = 20) {
return ["name" => $name, "age" => $age];
}
// Variadic functions
function sum(...$numbers) {
return array_sum($numbers);
}
// Arrow functions (PHP 7.4+)
$multiply = fn($a, $b) => $a * $b;
// Callback functions
function processUser($name, callable $callback) {
$user = ["name" => $name, "id" => time()];
return $callback($user);
}Anonymous Functions
Working with anonymous functions and closures
PHP
<?php
// Basic anonymous function
$greet = function($name) {
return "Hello, $name!";
};
// Using anonymous function
$result = $greet("Alice");
// Using with array_map
$numbers = [1, 2, 3, 4, 5];
$doubled = array_map(function($n) {
return $n * 2;
}, $numbers);
// Using with array_filter
$even = array_filter($numbers, function($n) {
return $n % 2 === 0;
});
// Arrow function (PHP 7.4+)
$multiply = fn($a, $b) => $a * $b;Object-Oriented Programming
Classes and Objects
Basic class and object usage
PHP
<?php
// Class definition
class User {
// Properties
private string $name;
private int $age;
// Constructor
public function __construct(string $name, int $age) {
$this->name = $name;
$this->age = $age;
}
// Methods
public function getName(): string {
return $this->name;
}
public function getAge(): int {
return $this->age;
}
public function greet(): string {
return "Hello, I'm {$this->name}";
}
}
// Creating objects
$user = new User("Alice", 25);
echo $user->getName(); // Alice
echo $user->greet(); // Hello, I'm AliceInheritance and Interfaces
Inheritance, interfaces, and abstract classes
PHP
<?php
// Interface
interface Logger {
public function log(string $message): void;
}
// Abstract class
abstract class BaseLogger implements Logger {
protected string $prefix;
public function __construct(string $prefix) {
$this->prefix = $prefix;
}
abstract protected function format(string $message): string;
}
// Concrete class
class FileLogger extends BaseLogger {
protected function format(string $message): string {
return "[{$this->prefix}] $message";
}
public function log(string $message): void {
$formatted = $this->format($message);
file_put_contents("log.txt", $formatted . PHP_EOL, FILE_APPEND);
}
}
// Using the classes
$logger = new FileLogger("INFO");
$logger->log("User logged in");Traits
Using traits for code reuse
PHP
<?php
// Trait definition
trait Timestampable {
private DateTime $createdAt;
public function setCreatedAt(DateTime $date): void {
$this->createdAt = $date;
}
public function getCreatedAt(): DateTime {
return $this->createdAt;
}
}
// Using trait
class Post {
use Timestampable;
private string $title;
public function __construct(string $title) {
$this->title = $title;
$this->setCreatedAt(new DateTime());
}
}
// Using the class
$post = new Post("Hello World");
echo $post->getCreatedAt()->format("Y-m-d H:i:s");Modern Features
Null Safe Operator
Using the null safe operator
PHP
<?php
// Null safe operator (PHP 8.0+)
$user = null;
$name = $user?->getName() ?? "Guest";
// Traditional way
$name = $user !== null ? $user->getName() : "Guest";
// Chaining
$country = $user?->getAddress()?->getCountry() ?? "Unknown";
// With arrays
$firstItem = $array?[0] ?? "default";Named Arguments
Using named arguments in PHP 8.0+
PHP
<?php
// Function with named arguments
function createUser(
string $name,
int $age = 20,
string $role = "user"
) {
return [
"name" => $name,
"age" => $age,
"role" => $role
];
}
// Using named arguments
$user = createUser(
name: "Alice",
role: "admin"
);
// Traditional way
$user = createUser("Alice", 20, "admin");Attributes
Using attributes in PHP 8.0+
PHP
<?php
// Attribute definition
#[Attribute]
class Route {
public function __construct(
public string $path,
public string $method = "GET"
) {}
}
// Using attributes
#[Route("/users", "GET")]
class UserController {
#[Route("/users/{id}", "GET")]
public function show(int $id) {
// ...
}
}
// Reading attributes
$reflection = new ReflectionClass(UserController::class);
$attributes = $reflection->getAttributes(Route::class);Database Operations
PDO Connection
Basic database operations with PDO
PHP
<?php
// Database connection
try {
$pdo = new PDO(
"mysql:host=localhost;dbname=mydb",
"username",
"password",
[
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
]
);
} catch (PDOException $e) {
die("Connection failed: " . $e->getMessage());
}
// Prepared statements
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$id]);
$user = $stmt->fetch();
// Named parameters
$stmt = $pdo->prepare("SELECT * FROM users WHERE name = :name");
$stmt->execute(["name" => $name]);
$user = $stmt->fetch();Transactions
Working with database transactions
PHP
<?php
try {
$pdo->beginTransaction();
// Multiple operations
$stmt1 = $pdo->prepare("INSERT INTO users (name) VALUES (?)");
$stmt1->execute([$name]);
$userId = $pdo->lastInsertId();
$stmt2 = $pdo->prepare("INSERT INTO profiles (user_id) VALUES (?)");
$stmt2->execute([$userId]);
$pdo->commit();
} catch (Exception $e) {
$pdo->rollBack();
throw $e;
}PHP - Interactive Developer Reference
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