PHP Functions Cheatsheet

Quick reference for PHP functions: string, array, date & time, math, file operations, sessions, cookies, and utility functions.

Function	Description	Example	Category
strlen()	Get string length	strlen("Hello");	String
strtoupper()	Convert to uppercase	strtoupper("hello");	String
strtolower()	Convert to lowercase	strtolower("HELLO");	String
substr()	Get substring	substr("Hello", 1, 3);	String
strpos()	Find position of substring	strpos("Hello","e");	String
count()	Count array elements	count([1,2,3]);	Array
array_push()	Add element to end	array_push($arr, 4);	Array
array_pop()	Remove last element	array_pop($arr);	Array
array_merge()	Merge arrays	array_merge($arr1, $arr2);	Array
in_array()	Check if exists	in_array(3, [1,2,3]);	Array
date()	Format date/time	date("Y-m-d H:i:s");	Date & Time
time()	Current timestamp	time();	Date & Time
strtotime()	Parse string to timestamp	strtotime("next Monday");	Date & Time
abs()	Absolute value	abs(-5);	Math
round()	Round float	round(3.14);	Math
ceil()	Round up	ceil(3.14);	Math
floor()	Round down	floor(3.14);	Math
rand()	Random number	rand(1,100);	Math
fopen()	Open file	fopen("file.txt","r");	File
fread()	Read file	fread($file, filesize("file.txt"));	File
fwrite()	Write file	fwrite($file, "Hello");	File
fclose()	Close file	fclose($file);	File
file_exists()	Check if file exists	file_exists("file.txt");	File
session_start()	Start session	session_start();	Session & Cookie
$_SESSION	Access session variable	$_SESSION["user"]="Alice";	Session & Cookie
setcookie()	Set cookie	setcookie("user","Alice",time()+3600);	Session & Cookie
$_COOKIE	Access cookie	$_COOKIE["user"];	Session & Cookie
print_r()	Print human-readable	print_r($arr);	Utility
var_dump()	Detailed variable info	var_dump($var);	Utility
die() / exit()	Terminate script	die("Error");	Utility