PHP Cheat Sheet

define("CURRENT\_DATE", date('Y-m-d')); // One possible representation echo CURRENT_DATE; # => 2021-01-05 # => CURRENT\_DATE is: 2021-01-05 echo 'CURRENT\_DATE is: ' . CURRENT_DATE; 

$str = "Visit Quickref.me"; echo preg\_match("/qu/i", $str); # => 1 

See: Regex in PHP

// As of PHP 8.0.0, this line: $result = $repo?->getUser(5)?->name; // Equivalent to the following code: if (is\_null($repo)) { $result = null; } else { $user = $repository->getUser(5); if (is\_null($user)) { $result = null; } else { $result = $user->name; } } 

See also: Nullsafe Operator

class MyException extends Exception { // do something } 

Usage

try { $condition = true; if ($condition) { throw new MyException('bala'); } } catch (MyException $e) { // Handle my exception } 

$nullableValue = null; try { $value = $nullableValue ?? throw new InvalidArgumentException(); } catch (InvalidArgumentException) { // Variable is optional // Handle my exception echo "print me!"; } 

try { // Do something } catch (Exception $e) { // Handle exception } finally { echo "Always print!"; } 

interface Foo { public function doSomething(); } interface Bar { public function doSomethingElse(); } class Cls implements Foo, Bar { public function doSomething() {} public function doSomethingElse() {} } 

class MyClass { // Object is treated as a String public function \_\_toString() { return $property; } // opposite to \_\_construct() public function \_\_destruct() { print "Destroying"; } } 

class MyClass { const MY\_CONST = 'value'; static $staticVar = 'static'; // Visibility public static $var1 = 'pubs'; // Class only private static $var2 = 'pris'; // The class and subclasses protected static $var3 = 'pros'; // The class and subclasses protected $var6 = 'pro'; // The class only private $var7 = 'pri'; } 

Access statically

echo MyClass::MY\_CONST; # => value echo MyClass::$staticVar; # => static 

class ExtendClass extends SimpleClass { // Redefine the parent method function displayVar() { echo "Extending class\n"; parent::displayVar(); } } $extended = new ExtendClass(); $extended->displayVar(); 

class Student { public function \_\_construct($name) { $this->name = $name; } public function print() { echo "Name: " . $this->name; } } $alex = new Student("Alex"); $alex->print(); # => Name: Alex 

$y = 1; $fn1 = fn($x) => $x + $y; // equivalent to using $y by value: $fn2 = function ($x) use ($y) { return $x + $y; }; echo $fn1(5); # => 6 echo $fn2(5); # => 6 

function coffee($type = "cappuccino") { return "Making a cup of $type.\n"; } # => Making a cup of cappuccino. echo coffee(); # => Making a cup of . echo coffee(null); # => Making a cup of espresso. echo coffee("espresso"); 

function recursion($x) { if ($x < 5) { echo "$x"; recursion($x + 1); } } recursion(1); # => 1234 

$greet = function($name) { printf("Hello %s\r\n", $name); }; $greet('World'); # => Hello World $greet('PHP'); # => Hello PHP 

function bar($arg = '') { echo "In bar(); arg: '$arg'.\n"; } $func = 'bar'; $func('test'); # => In bar(); arg: test 

// Available in PHP 7.1 function voidFunction(): void { echo 'Hello'; return; } voidFunction(); # => Hello 

// Available in PHP 7.1 function nullOrString(int $v) : ?string { return $v % 2 ? "odd" : null; } echo nullOrString(3); # => odd var\_dump(nullOrString(4)); # => NULL 

See: Nullable types

// Basic return type declaration function sum($a, $b): float {/\*...\*/} function get\_item(): string {/\*...\*/} class C {} // Returning an object function getC(): C { return new C; } 

function square($x) { return $x * $x; } echo square(4); # => 16 

$a = ['foo' => 1, 'bar' => 2]; # => 12 foreach ($a as $k) { echo $k; } 

See: Array iteration

# => 1235 for ($i = 1; $i <= 5; $i++) { if ($i === 4) { continue; } echo $i; } 

# => 123 for ($i = 1; $i <= 5; $i++) { if ($i === 4) { break; } echo $i; } 

# => 12345 for ($i = 1; $i <= 5; $i++) { echo $i; } 

$i = 1; # => 12345 do { echo $i++; } while ($i <= 5); 

$i = 1; # => 12345 while ($i <= 5) { echo $i++; } 

$age = 23; $result = match (true) { $age >= 65 => 'senior', $age >= 25 => 'adult', $age >= 18 => 'young adult', default => 'kid', }; echo $result; # => young adult 

$statusCode = 500; $message = match($statusCode) { 200, 300 => null, 400 => 'not found', 500 => 'server error', default => 'known status code', }; echo $message; # => server error 

See: Match

# => Does print (false ? 'Not' : 'Does'); $x = false; # => Does print($x ?: 'Does'); $a = null; $b = 'Does print'; # => a is unset echo $a ?? 'a is unset'; # => print echo $b ?? 'b is unset'; 

$x = 0; switch ($x) { case '0': print "it's zero"; break; case 'two': case 'three': // do something break; default: // do something } 

$a = 10; $b = 20; if ($a > $b) { echo "a is bigger than b"; } elseif ($a == $b) { echo "a is equal to b"; } else { echo "a is smaller than b"; } 

function foo($first, ...$other) { var\_dump($first); # => a var\_dump($other); # => ['b', 'c'] } foo('a', 'b', 'c' /\*, ...\*/ ); // or function foo($first, string ...$other){} 

$array = [1, 2]; function foo(int $a, int $b) { echo $a; # => 1 echo $b; # => 2 } foo(...$array); 

$a = [1, 2]; $b = [3, 4]; // PHP 7.4 later # => [1, 2, 3, 4] $result = [...$a, ...$b]; 

$arr = ["foo" => "bar", "bar" => "foo"]; foreach ( $arr as $key => $value ) { echo "key: " . $key . "\n"; echo "val: {$arr[$key]}\n"; } 

$colors = array('red', 'blue', 'green'); foreach ($colors as $color) { echo "Do you like $color?\n"; } 

$array = array('a', 'b', 'c'); $count = count($array); for ($i = 0; $i < $count; $i++) { echo "i:{$i}, v:{$array[$i]}\n"; } 

$array = array( "foo" => "bar", 42 => 24, "multi" => array( "dim" => array( "a" => "foo" ) ) ); # => string(3) "bar" var\_dump($array["foo"]); # => int(24) var\_dump($array[42]); # => string(3) "foo" var\_dump($array["multi"]["dim"]["a"]); 

$multiArray = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], ]; print\_r($multiArray[0][0]) # => 1 print\_r($multiArray[0][1]) # => 2 print\_r($multiArray[0][2]) # => 3 

$a1 = ["hello", "world", "!"] $a2 = array("hello", "world", "!"); $a3 = explode(",", "apple,pear,peach"); 

#Mixed int and string keys

$array = array( "foo" => "bar", "bar" => "foo", 100 => -100, -100 => 100, ); var\_dump($array); 

#Short array syntax

$array = [ "foo" => "bar", "bar" => "foo", ]; 

$s = "Hello Phper"; echo strlen($s); # => 11 echo substr($s, 0, 3); # => Hel echo substr($s, 1); # => ello Phper echo substr($s, -4, 3);# => hpe echo strtoupper($s); # => HELLO PHPER echo strtolower($s); # => hello phper echo strpos($s, "l"); # => 2 var\_dump(strpos($s, "L")); # => false 

See: String Functions

$str = "foo"; // Uninterpolated multi-liners $nowdoc = <<<'END' Multi line string $str END; // Will do string interpolation $heredoc = <<<END Multi line $str END; 

# => '$String' $sgl\_quotes = '$String'; # => 'This is a $String.' $dbl\_quotes = "This is a $sgl\_quotes."; # => a tab character. $escaped = "a \t tab character."; # => a slash and a t: \t $unescaped = 'a slash and a t: \t'; 

function bar(): iterable { return [1, 2, 3]; } function gen(): iterable { yield 1; yield 2; yield 3; } foreach (bar() as $value) { echo $value; # => 123 } 

$a = null; $b = 'Hello php!'; echo $a ?? 'a is unset'; # => a is unset echo $b ?? 'b is unset'; # => Hello php $a = array(); $a == null # => true $a === null # => false is\_null($a) # => false 

$float1 = 1.234; $float2 = 1.2e7; $float3 = 7E-10; $float4 = 1\_234.567; // as of PHP 7.4.0 var\_dump($float4); // float(1234.567) $float5 = 1 + "10.5"; # => 11.5 $float6 = 1 + "-1.3e3"; # => -1299 

$int1 = 28; # => 28 $int2 = -32; # => -32 $int3 = 012; # => 10 (octal) $int4 = 0x0F; # => 15 (hex) $int5 = 0b101; # => 5 (binary) # => 2000100000 (decimal, PHP 7.4.0) $int6 = 2\_000\_100\_000; 

See also: Integers

$boolean1 = true; $boolean2 = TRUE; $boolean3 = false; $boolean4 = FALSE; $boolean5 = (boolean) 1; # => true $boolean6 = (boolean) 0; # => false 

Boolean are case-insensitive

class Student { public function \_\_construct($name) { $this->name = $name; } } $alex = new Student("Alex"); 

See: Classes

const MY\_CONST = "hello"; echo MY_CONST; # => hello # => MY\_CONST is: hello echo 'MY\_CONST is: ' . MY_CONST; 

# This is a one line shell-style comment // This is a one line c++ style comment /\* This is a multi line comment yet another line of comment \*/ 

function add($num1, $num2 = 1) { return $num1 + $num2; } echo add(10); # => 11 echo add(10, 5); # => 15 

See: Functions

#vars.php

<?php // begin with a PHP open tag. $fruit = 'apple'; echo "I was imported"; return 'Anything you like.'; ?> 

#test.php

<?php include 'vars.php'; echo $fruit . "\n"; # => apple /\* Same as include, cause an error if cannot be included\*/ require 'vars.php'; // Also works include('vars.php'); require('vars.php'); // Include through HTTP include 'http://x.com/file.php'; // Include and the return statement $result = include 'vars.php'; echo $result; # => Anything you like. ?> 

$x = 1; $y = 2; $sum = $x + $y; echo $sum; # => 3 

See: Operators

$num = [1, 3, 5, 7, 9]; $num[5] = 11; unset($num[2]); // Delete variable print\_r($num); # => 1 3 7 9 11 echo count($num); # => 5 

See: Arrays

$url = "quickref.me"; echo "I'm learning PHP at $url"; // Concatenate strings echo "I'm learning PHP at " . $url; $hello = "Hello, "; $hello .= "World!"; echo $hello; # => Hello, World! 

See: Strings

$boolean1 = true; $boolean2 = True; $int = 12; $float = 3.1415926; unset($float); // Delete variable $str1 = "How are you?"; $str2 = 'Fine, thanks'; 

See: Types

<?php // begin with a PHP open tag. echo "Hello World\n"; print("Hello quickref.me"); ?> 

PHP run command

$ php hello.php