PHP Cheatsheet

<?php
// Single line comment
# Another comment
/* Multi-line
   comment */
echo "Hello, World!";
?>

$a = 1;
$b = "Hello";
$c = true;
$d = null;
$e = [1, 2, 3];
$f = ["name" => "John", "age" => 25];

$a = 1;        // Integer
$b = 2.5;     // Float
$c = 'A';     // String
$d = true;    // Boolean
$e = [1,2,3]; // Array
$f = null;    // Null

$s = "Hello";
$s2 = 'World';
$len = strlen($s);
$upper = strtoupper($s);
$name = "Alice";
$msg = "Hi, $name!";

$a = 5;
$b = 2.5;
$sum = $a + $b;
$pow = pow($a, 2);
$parsed = intval("42");

$arr = [1, 2, 3];
$assoc = ["a" => 1, "b" => 2];
$multi = [[1,2], [3,4]];
echo $arr[0];
echo $assoc["a"];

$arr = [1, 2, 3];
array_push($arr, 4);
$len = count($arr);
$sum = array_sum($arr);
$keys = array_keys($arr);
$vals = array_values($arr);

if ($a > 0) {
  echo "Positive";
} elseif ($a == 0) {
  echo "Zero";
} else {
  echo "Negative";
}

for ($i = 0; $i < 5; $i++) {
  echo $i;
}
while ($a > 0) {
  $a--;
}
switch ($a) {
  case 1:
    echo "One";
    break;
  default:
    break;
}

function add($a, $b) {
  return $a + $b;
}
function greet($name = "World") {
  echo "Hello, $name!";
}

$_GET["q"];
$_POST["name"];
$_SESSION["user"];
$_COOKIE["id"];
$_SERVER["REQUEST_URI"];
$_FILES["file"];

<form method="post" action="">
  <input type="text" name="name" />
  <input type="submit" value="Send" />
</form>
$name = $_POST["name"] ?? "";

$s = "Hello World";
$len = strlen($s);
$pos = strpos($s, "W");
$rep = str_replace("World", "PHP", $s);
$parts = explode(" ", $s);

$now = date("Y-m-d H:i:s");
$ts = time();
$dt = new DateTime();
echo $dt->format("Y-m-d");

$txt = file_get_contents("file.txt");
file_put_contents("file.txt", "Hello");
$lines = file("file.txt");

include "file.php";
require "file.php";
include_once "file.php";
require_once "file.php";

session_start();
$_SESSION["user"] = "Alice";
$user = $_SESSION["user"] ?? null;

setcookie("user", "Alice", time()+3600);
$user = $_COOKIE["user"] ?? null;

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

class User {
  private $name;
  private $age;

  public function __construct($name, $age) {
    $this->name = $name;
    $this->age = $age;
  }

  public function getName() {
    return $this->name;
  }

  public function getAge() {
    return $this->age;
  }
}

$user = new User("John", 25);
echo $user->getName();

class User {
  private $name;
  private $age;

  public function __construct($name, $age) {
    $this->name = $name;
    $this->age = $age;
  }

  public function getName() {
    return $this->name;
  }

  public function getAge() {
    return $this->age;
  }
}

$user = new User("John", 25);
echo $user->getName();

class Animal {
  protected $name;

  public function __construct($name) {
    $this->name = $name;
  }

  public function getName() {
    return $this->name;
  }
}

class Dog extends Animal {
  private $breed;

  public function __construct($name, $breed) {
    parent::__construct($name);
    $this->breed = $breed;
  }

  public function getBreed() {
    return $this->breed;
  }
}

$dog = new Dog("Buddy", "Golden Retriever");
echo $dog->getName(); // Outputs: Buddy
echo $dog->getBreed(); // Outputs: Golden Retriever

interface Animal {
  public function makeSound();
}

class Dog implements Animal {
  public function makeSound() {
    echo "Woof!";
  }
}

$dog = new Dog();
$dog->makeSound(); // Outputs: Woof!

trait Greet {
  public function sayHello() {
    echo "Hello from trait!";
  }
}

class User {
  use Greet;
}

$user = new User();
$user->sayHello(); // Outputs: Hello from trait!

namespace App;

class User {
  public function getName() {
    return "User from namespace";
  }
}

$user = new User();
echo $user->getName(); // Outputs: User from namespace

$dsn = "mysql:host=localhost;dbname=test";
$username = "root";
$password = "";

try {
  $pdo = new PDO($dsn, $username, $password);
  $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  $stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
  $stmt->execute([1]);
  $user = $stmt->fetch(PDO::FETCH_ASSOC);
  print_r($user);
} catch (PDOException $e) {
  echo "Connection failed: " . $e->getMessage();
}

$mysqli = new mysqli("localhost", "root", "", "test");

if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: " . $mysqli->connect_error;
  exit();
}

$stmt = $mysqli->prepare("SELECT * FROM users WHERE id = ?");
$stmt->bind_param("i", 1);
$stmt->execute();
$result = $stmt->get_result();
$user = $result->fetch_assoc();
print_r($user);

$stmt->close();
$mysqli->close();

$data = ['name' => 'John', 'age' => 25];
$json = json_encode($data);
echo $json; // Outputs: {"name":"John","age":25}

$decoded = json_decode($json);
print_r($decoded); // Outputs: Array ( [name] => John [age] => 25 )

$name = "John Doe";
$filtered_name = filter_var($name, FILTER_SANITIZE_STRING);
echo $filtered_name; // Outputs: John Doe

$email = "test@example.com";
$email_filtered = filter_var($email, FILTER_SANITIZE_EMAIL);
echo $email_filtered; // Outputs: test@example.com

$url = "http://example.com?q=test";
$url_filtered = filter_var($url, FILTER_SANITIZE_URL);
echo $url_filtered; // Outputs: http://example.com?q=test

$email = "test@example.com";
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo "Valid email address!";
} else {
  echo "Invalid email address.";
}

$age = "25";
if (filter_var($age, FILTER_VALIDATE_INT, ["options" => ["min_range" => 0, "max_range" => 100]])) {
  echo "Valid age!";
} else {
  echo "Invalid age.";
}

print_r($_SERVER); // Prints all server variables

$dir = ".";
$files = array_diff(scandir($dir), array('.', '..'));
$files = array_values($files);
print_r($files);

$path = "test.txt";
if (file_exists($path)) {
  echo "File exists.";
} else {
  echo "File does not exist.";
}

$size = filesize("test.txt");
echo "File size: " . $size . " bytes";

$modified = filemtime("test.txt");
echo "Last modified: " . date("Y-m-d H:i:s", $modified);

$content = file_get_contents("test.txt");
echo $content;

$content = "Hello, World!";
file_put_contents("test.txt", $content);

$lines = file("test.txt");
print_r($lines);

$content = "Hello\nWorld\n";
$lines = explode("\n", $content);
print_r($lines);

$content = "Hello, World!";
$encoded = base64_encode($content);
echo $encoded;

$decoded = base64_decode($encoded);
echo $decoded;

$hash = password_hash("password123", PASSWORD_DEFAULT);
echo $hash;

if (password_verify("password123", $hash)) {
  echo "Password is correct.";
} else {
  echo "Password is incorrect.";
}

$random_bytes = random_bytes(10);
echo bin2hex($random_bytes);

$random_int = random_int(1, 100);
echo $random_int;