PHP Cheat Sheet

Learn PHP from the basics →

Variables

$name = "value";: Declare a variable
"Hello, $name": String interpolation (double quotes only)
gettype($x): Get a variable's type

Arrays

[1, 2, 3]: Indexed array
["k" => "v"]: Associative array
count($arr): Array length
array_map($fn, $arr): Transform each element
array_filter($arr, $fn): Keep matching elements

Strings

strlen($s): String length
strtolower($s) / strtoupper($s): Change case
str_contains($s, $needle): Check for a substring
trim($s): Remove surrounding whitespace
explode(",", $s): Split into an array

Control Flow

if / elseif / else: Conditional branching
foreach ($arr as $k => $v): Loop with key and value
match ($x) { 1 => "one", default => "?" }: PHP 8 match expression

Functions

function f(string $x): string { }: Typed function
fn ($x) => $x * 2: Arrow function
f(name: "Ada"): Named argument

Classes

class User { public function __construct(public string $name) {} }: Constructor property promotion
new User("Ada"): Instantiate
$user->name: Access a property
interface Payable { public function pay(): void; }: Interface
enum Status { case Active; case Inactive; }: Enum (PHP 8.1+)

Errors & Database

try { } catch (Exception $e) { }: Exception handling
new PDO($dsn, $user, $pass): Connect to a database
$stmt = $pdo->prepare("... WHERE id = ?"); $stmt->execute([$id]);: Parameterized query