PHP cheat sheet (updated to PHP 8.1)

php -S localhost:3000 

// one line comment /* This is a multiple-lines comment block that spans over multiple lines */ 

// PHP opening/closing tag <?php echo "Hello World"; ?> // if no closing tag the rest of the file will be considered PHP // Short syntax for PHP echo <?= "Hello World" ?> //Enable strict typing (first line of your PHP file) <? declare(strict_types=1); // Include a PHP file require 'app/Product.php' // Create a namespace namespace App; // Use a namespace use App\Product; $firstName = 'Mike' // camelCase function updateProduct() // camelCase class ProductItem // StudlyCaps const ACCESS_KEY = '123abc'; // all upper case with underscore separators 

echo 'Hello World'; // Debug output var_dump($names); print_r($products); // Input from console $name = readline('What is your name : '); 

$name = 'Mike'; //string $isActive = true; //boolean $number = 25; //integer $amount = 99.95; //float $fruits = ['orange', 'apple', 'banana'] //array const MAX_USERS = 50; //constant define('MAX_USERS', 50); //constant // Assign 'by reference' with the & keyword $name_2 = &$name_1 // Type conversion $age = (int)readline('Your age: '); echo 'Your age is' . (string)$age; echo gettype($age); // int echo is_int($age) // true echo is_float(12.5) // true echo is_string($name) // true 

// String can use single quote $name = 'Mike' // or double quote $name = "Mike" // Double quote string can escape characters \n = new line \t = tab \\ = backslash echo "Hello Mike\nHello David"; // Double quote string can do interpolation echo "Hello $name"; // string concat echo 'Hello ' . $name; // string length echo strlen($name); // Remove space(s) before and after echo trim($text) // Convert to lowercase / uppercase echo strtolower($email); echo strtoupper($name); // Converts the first character to uppercase echo ucfirst($name); // 'Mike'  // Replace text a by text b in $text echo str_replace('a', 'b', $text); // String Contains (PHP 8) echo str_contains($name, 'ke') # true // Find numeric position of first occurrence  $pos = strpos($name, 'k'); # 2 // Returns portion of string (offset / length) echo substr($name, 0, $pos); # Mi  

 // Shortcut addition assignment $value = 10 $value++ // 11 // or $value += 1 // 11 // Shortcut subtraction assignment $value = 10 $value-- // 9 // or $value -= 1 // 9 // Check if numeric echo is_numeric('59.99'); # true // Round a number echo round(0.80); // returns 1 // Round a number with precision echo round(1.49356, 2)); // returns 1.49 // Random number  echo(rand(10, 100)); # 89 

// If / elseif / else if ($condition == 10) { echo 'condition 10' } elseif ($condition == 5) { echo 'condition 5' } else { echo 'all other conditions' } // And condition = && if ($condition === 10 && $condition2 === 5) { echo '10 and 5' } // Or condition = || if ($condition === 10 || $condition2 === 5) { echo '10 or 5' } // One line  if ($isActive) return true; // Null check if (is_null($name)) { do something... } //Comparaison operation == // equal no type check === // equal with type check != //not equal || //or && //and > //greater than < //less than // Ternary operator (true : false) echo $isValid ? 'user valid' : 'user not valid'; //Null Coalesce Operator echo $name ?? 'Mike'; //output 'Mike' if $name is null //Null Coalesce Assignment $name ??= 'Mike'; // Null Safe Operator (PHP 8) will return null if one ? is null echo $user?->profile?->activate(); // Null Safe + Null Coalesce (if null will return 'No user profile') echo $user?->profile?->activate() ?? 'Not applicable'; //Spaceship operator return -1 0 1 $names = ['Mike', 'Paul', 'John'] usort($names, function($a, $b) { return $a <=> $b; } // ['John', 'Mike', 'Paul'] // Return false when convert as boolean false, 0, 0.0, null, unset, '0', '', [] // Compare same variable with multiple values switch ($color) { case 'red': echo 'The color is red'; break; case 'yellow': echo 'The color is yellow'; break; case 'blue': echo 'The color is blue'; break; default: echo 'The color is unknown'; } // Match Expression (PHP 8) $type = match($color) { 'red' => 'danger', 'yellow', 'orange' => 'warning', 'green' => 'success', default => 'Unknown' }; // Check if variable declare isset($color['red']); # true 

//for loop for ($i = 0; $i < 20; $i++) { echo "i value = " . i; } //while loop $number = 1; while ($number < 10) { echo 'value : ' . $number ; $number += 1; } //do while $number = 1; do { echo 'value : ' . $number ; $number += 1; } while ($number < 10); // foreach with break / continue exemple $values = ['one', 'two', 'three']; foreach ($values as $value) { if ($value === 'two') { break; // exit loop } elseif ($value === 'three') { continue; // next loop iteration } } 

//Array declaration can contain any types $example = ['Mike', 50.2, true, ['10', '20']]; //Array declaration $names = ['Mike', 'Peter', 'Shawn', 'John']; // Direct access to a specific element $name[1] //output Peter // How to access an array in an array $example[3][1] // 20 //add a element to an array $names[] = 'Micheal'; // Array merge $array3 = array_merge($array1, $array2); // Merge with spreading operator (also work with associative array) $array3 = [...$array1, ...$array2]; // Array Concat with Spread Operator $names = ['Mike', 'Peter', 'Paul']; $people = ['John', ...$names]; // ['John', 'Mike', 'Peter', 'Paul'] //Remove array entry: unset($names['Peter']); //Array to string echo implode(', ', $names) //output Mike, Shawn, John, Micheal // String to Array echo explode(',', $text); // ['Mike', 'Shawn', 'John'] //loop for each array entry foreach($names as $name) { echo 'Hello ' . $name; } // Number of items in a Array echo count($names); //Associative array declaration (key => value): $person = ['age' => 45, 'genre' => 'men']; //Add to ass. array: $person['name'] = 'Mike'; //loop ass. array key => value:  foreach($names as $key => $value) { echo $key . ' : ' . $value } // Check if a specific key exist echo array_key_exists('age', $person); // Return keys echo array_keys($person); // ['age', 'genre'] // Return values echo array_values($person) // [45, 'men'] //Array filter (return a filtered array) $filteredPeople = array_filter($people, function ($person) { return $names->active; }) // Array map (return transform array): $onlyNames = array_map(function($person) { return ['name' => $person->name]; }, $people) # Search associative array $items = [ ['id' => '100', 'name' => 'product 1'], ['id' => '200', 'name' => 'product 2'], ['id' => '300', 'name' => 'product 3'], ['id' => '400', 'name' => 'product 4'], ]; # search all value in the 'name' column $found_key = array_search('product 3', array_column($items, 'name')); # return 2 

//function declararion function name($firstName, $lastName = 'defaultvalue') { return "$firstName $lastName" } //function call name('Mike', 'Taylor'); //function call with named parameters (PHP 8) name(firstName: 'Mike', lastName: 'Taylor'); // order can change //function variables params function name(...$params) { return $params[0] . “ “ . params[1]; } // Closure function Route::get('/', function () { return view('welcome'); }); // Arrow functions Route::get('/', fn () => view('welcome'); // Typed parameter and typed return function display(string $first, string $last) : string { return "$first $last"; } // Typed or null function display(?string $name) { ... } // Union type (or) function display(string|int $data) { ... } // Intersection type (and) function count_and_interate(Iterator&Countable $value) { ... } // Return any type (mixed) function logInfo(string $info) : mixed { ... } // No return (void) function logInfo(string $info) : void { ... } 

// Declaration enum InvoiceStatus { case Sent; case Paid; case Cancelled; } // The enum can then be use as a type function printInvoiceStatus(InvoiceStatus $status) { print($status->name); } printInvoiceStatus(InvoiceStatus::Sent); // Sent // enum with return value and public function exemple enum InvoiceStatus : int { case Sent = 0; case Paid = 1; case Cancelled = 2; public function text() : string { return match ($this) { self::Sent => 'Sent', self::Paid => 'Paid', self::Cancelled => 'Cancelled' }; } } function getInvoiceStatus(InvoiceStatus $status) { print($status->text()); print($status->value); } getInvoiceStatus(InvoiceStatus::Paid); // Paid1 

// Get the current dir $current_dir = __DIR__; // Check if file exist if (file_exists('/posts/first.txt')) { do some stuff } // Read file content into one variable $post = file_get_contents($file); //File read $file = fopen("test.txt", "r"); //Output lines until EOF is reached while(! feof($file)) { $line = fgets($file); echo $line. "<br>"; } fclose($file); // File write (csv) $file = fopen('export.csv', 'a'); $array = ['name' => 'Mike', 'age' => 45]; //Write key name as csv header fputcsv($file, array_keys($array[0])); //Write lines (format as csv) foreach ($array as $row) { fputcsv($file, $row); } fclose($file); 

//Throw Error if (someCondition) { throw new Exception('Data format error'); } //Catch the Error try { $db->checkData($data); } catch (Exception $e) { echo $e->getMessage(); } 

//class declaration class Person { } // object instantiation $person = new Person //class properties and constructor class Person { protected $firstName; protected $lastName; public function __construct($firstName, $lastName) { $this->firstName = $firstName; $this->lastName = $lastName } // Constructor Property Promotion (PHP 8) class Person { public function __construct(protected $firstName, protected $lastName) { } // Getter and Setter class Person { private $name; public function setName($name){ if(!is_string($name)){ throw new Exception('$name must be a string!'); } $this->name = $name; } public function getName(){ return $this->name; } } // Readonly properties (PHP 8.1) class Person { public function __construct( public readonly string $firstName, public readonly string $lastName ) { } } //static constructor public static function create(...$params) { return new self($params) } $person = Person::create(‘Mike’, ‘Taylor’); // Static Method class greeting { public static function welcome() { echo "Hello World!"; } } // Call static method greeting::welcome(); // Static method call class greeting { public static function welcome() { echo "Hello World!"; } public function __construct() { static::welcome(); } } new greeting(); // Static constant class Connection { const MAX_USER = 100; } echo Connection::MAX_USER # 100 // class inheritance class Customer extends Person { public function name() { parent::name(); echo 'Override method'; } } // self keyword reference current class (not modify by inheritance late binding like static will be) self::welcome(); // Interface interface Animal { public function makeSound(); } class Cat implements Animal { public function makeSound() { echo "Meow"; } } $animal = new Cat(); $animal->makeSound(); //Trait (mix-in) trait HelloWorld { public function sayHello() { echo 'Hello World!'; } } class Greetings { use HelloWorld; } $object = new Greetings(); $object->sayHello();