PHP Cheat Sheet

PHP is a widely used server-side scripting language designed for web development and general-purpose programming. This PHP cheatsheet is a structured, example-driven reference covering core syntax, arrays, functions, object-oriented features, and common PHP APIs.

Basic Script Structure

<?php
echo "Hello, PHP";

Running PHP

php script.php

Variables

$a = 10;
$b = "text";
$c = true;

Data Types

int
float
string
bool
array
object
null

gettype($a);

Strings

$s = "PHP";

strlen($s);
strtoupper($s);
strpos($s, "P");

$name = "World";
echo "Hello $name";

Operators

$a + $b;
$a - $b;
$a * $b;
$a / $b;
$a % $b;

$a == $b;
$a === $b;
$a != $b;
$a !== $b;

$a && $b;
$a || $b;
!$a;

Control Flow

if / else

if ($a > 10) {
    $r = 1;
} else {
    $r = 0;
}

switch

switch ($a) {
    case 1:
        break;
    default:
        break;
}

Loops

for ($i = 0; $i < 5; $i++) {
    echo $i;
}

while ($a > 0) {
    $a--;
}

foreach ($arr as $value) {
    echo $value;
}

foreach ($arr as $key => $value) {
    echo $key;
}

Functions

function add(int $a, int $b): int {
    return $a + $b;
}

$r = add(2, 3);

Default Parameters

function multiply(int $a, int $b = 2): int {
    return $a * $b;
}

Variadic Functions

function total(int ...$nums): int {
    return array_sum($nums);
}

Arrays

Indexed Arrays

$arr = [1, 2, 3];
$arr[] = 4;

Associative Arrays

$map = [
    "a" => 1,
    "b" => 2
];

Array Functions

count($arr);
array_push($arr, 5);
array_pop($arr);

array_map(fn($n) => $n * 2, $arr);
array_filter($arr, fn($n) => $n > 1);

Classes

class Counter {
    private int $value = 0;

    public function increment(): void {
        $this->value++;
    }

    public function get(): int {
        return $this->value;
    }
}

Creating Objects

$c = new Counter();
$c->increment();

Constructors

class Point {
    public function __construct(
        public int $x,
        public int $y
    ) {}
}

Inheritance

class Animal {
    public function speak() {}
}

class Dog extends Animal {
}

Interfaces

interface Logger {
    public function log(string $msg): void;
}

class ConsoleLogger implements Logger {
    public function log(string $msg): void {
        echo $msg;
    }
}

Abstract Classes

abstract class Shape {
    abstract public function area(): float;
}

Traits

trait Timestamped {
    public function now(): int {
        return time();
    }
}

class Item {
    use Timestamped;
}

Namespaces

namespace App\Utils;

function add(int $a, int $b): int {
    return $a + b;
}

use App\Utils;

Exceptions

try {
    throw new Exception("fail");
} catch (Exception $e) {
    echo $e->getMessage();
} finally {
}

File I/O

file_put_contents("file.txt", "text");
$content = file_get_contents("file.txt");

JSON

$data = ["a" => 1];
$json = json_encode($data);
$decoded = json_decode($json, true);

Date & Time

$date = new DateTime();
echo $date->format("Y-m-d");

Superglobals

$_GET;
$_POST;
$_SERVER;
$_SESSION;
$_COOKIE;