value}";
$msg = 'No interpolation in ' . $name . ' single quotes';

// Heredoc
$text = <<

function greet(string $name, int $age = 18): string {
    return "Hello $name, age $age";
}

// Type declarations (PHP 7+)
function add(int $a, int $b): int { return $a + $b; }
function nullable(?string $s): ?string { return $s; }

// Variadic
function sum(int ...$nums): int { return array_sum($nums); }
sum(1, 2, 3, 4, 5);  // 15

// First-class callable (PHP 8.1)
$fn = strlen(...);
$lengths = array_map(strlen(...), ['hello', 'world']);

// Arrow functions (PHP 7.4)
$multiply = fn($x) => $x * 2;
$square   = fn($x) => fn($y) => $x * $y;  // currying

// Anonymous functions (closures)
$greet = function(string $name) use ($prefix): string {
    return "$prefix $name";   // capture $prefix from scope
};

// Match expression (PHP 8.0)
$result = match($status) {
    'active' => 'green',
    'inactive', 'banned' => 'red',
    default => 'gray',
};

// Indexed array
$fruits = ['apple', 'banana', 'cherry'];
$fruits[] = 'date';          // append
count($fruits);              // 4

// Associative array
$user = [
    'name'  => 'Ali',
    'email' => 'ali@test.com',
    'age'   => 22,
];
$user['role'] = 'admin';
unset($user['age']);

// Multidimensional
$matrix = [[1,2,3],[4,5,6],[7,8,9]];
$users = [
    ['id'=>1,'name'=>'Ali'],
    ['id'=>2,'name'=>'Sara'],
];

// Array functions
array_push($arr, 'item');       array_pop($arr);
array_shift($arr);              array_unshift($arr, 'item');
array_merge($a, $b);           array_combine($keys, $vals);
array_slice($arr, 1, 3);       array_splice($arr, 1, 2);
array_search('val', $arr);     in_array('val', $arr);
array_key_exists('key', $arr); isset($arr['key']);
sort($arr);   rsort($arr);    usort($arr, fn($a,$b) => $a<=>$b);
array_map(fn($x)=>$x*2, $arr);
array_filter($arr, fn($x)=>$x>3);
array_reduce($arr, fn($carry,$x)=>$carry+$x, 0);
array_unique($arr);  array_flip($arr);  array_reverse($arr);
array_column($users, 'name');   // extract column

class BankAccount {
    private float $balance;
    protected string $owner;
    public static int $count = 0;

    public function __construct(string $owner, float $initial = 0) {
        $this->owner   = $owner;
        $this->balance = $initial;
        self::$count++;
    }

    public function deposit(float $amount): void {
        if ($amount > 0) $this->balance += $amount;
    }

    public function getBalance(): float { return $this->balance; }

    // Magic methods
    public function __toString(): string {
        return "{$this->owner}: \${$this->balance}";
    }

    public static function getCount(): int { return self::$count; }
}

class SavingsAccount extends BankAccount {
    private float $interestRate;

    public function __construct(string $owner, float $rate) {
        parent::__construct($owner);
        $this->interestRate = $rate;
    }

    public function addInterest(): void {
        $this->deposit($this->balance * $this->interestRate);
    }
}

$acc = new BankAccount('Ali', 1000);
$acc->deposit(500);
echo $acc;  // Ali: $1500

// Interface — contract
interface Printable {
    public function print(): void;
    public function getContent(): string;
}

interface Saveable {
    public function save(string $path): bool;
}

class Document implements Printable, Saveable {
    public function __construct(private string $content) {}
    public function print(): void { echo $this->content; }
    public function getContent(): string { return $this->content; }
    public function save(string $path): bool { return file_put_contents($path, $this->content) !== false; }
}

// Trait — reusable code snippets
trait Timestamps {
    private ?DateTime $createdAt = null;
    private ?DateTime $updatedAt = null;

    public function touch(): void { $this->updatedAt = new DateTime(); }
    public function getCreatedAt(): ?DateTime { return $this->createdAt; }
}

trait SoftDelete {
    private ?DateTime $deletedAt = null;
    public function delete(): void { $this->deletedAt = new DateTime(); }
    public function isDeleted(): bool { return $this->deletedAt !== null; }
}

class Post {
    use Timestamps, SoftDelete;  // use multiple traits!
    public function __construct(public string $title) {}
}

 120) $errors[] = 'Age must be 0-120';

// Prevent XSS
$safe_name = htmlspecialchars($name, ENT_QUOTES, 'UTF-8');

// CSRF protection
session_start();
if (empty($_SESSION['csrf_token'])) {
    $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
}
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (!hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {
        die('CSRF token mismatch');
    }
}
?>

 PDO::ERRMODE_EXCEPTION,
         PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC]
    );
} catch (PDOException $e) {
    die('Connection failed: ' . $e->getMessage());
}

// Prepared statement (ALWAYS use for user input — prevents SQL injection!)
$stmt = $pdo->prepare('SELECT * FROM users WHERE email = ? AND active = ?');
$stmt->execute([$email, 1]);
$user = $stmt->fetch();          // one row
$users = $stmt->fetchAll();      // all rows

// Named placeholders
$stmt = $pdo->prepare('INSERT INTO users (name, email) VALUES (:name, :email)');
$stmt->execute(['name' => $name, 'email' => $email]);
$newId = $pdo->lastInsertId();

// Update / Delete
$pdo->prepare('UPDATE users SET age = ? WHERE id = ?')->execute([$age, $id]);
$pdo->prepare('DELETE FROM users WHERE id = ?')->execute([$id]);

// Transaction
$pdo->beginTransaction();
try { /* operations */ $pdo->commit(); }
catch (Exception $e) { $pdo->rollBack(); throw $e; }

'Ali','role'=>'admin'];
unset($_SESSION['temp']);
session_destroy();  // logout

// Secure session config (php.ini or runtime)
ini_set('session.cookie_httponly', 1);    // no JS access
ini_set('session.cookie_secure', 1);      // HTTPS only
ini_set('session.cookie_samesite', 'Strict');

// Cookies — client-side
setcookie(
    'remember_token',
    $token,
    time() + (30 * 24 * 60 * 60),  // 30 days
    '/',     // path
    '',      // domain
    true,    // secure (HTTPS only)
    true     // httponly (no JS access)
);

$token = $_COOKIE['remember_token'] ?? null;

// Delete cookie
setcookie('remember_token', '', time() - 3600);

# Composer — PHP package manager
composer init                    # create composer.json
composer require laravel/laravel # install package
composer update                  # update all
composer install                 # install from composer.lock
composer dump-autoload           # regenerate autoload

# Laravel — the most popular PHP framework
composer create-project laravel/laravel myapp
cd myapp && php artisan serve    # dev server

# Artisan commands
php artisan make:model User -m   # model + migration
php artisan make:controller UserController --resource
php artisan make:request StoreUserRequest
php artisan make:middleware Authenticate
php artisan migrate              # run migrations
php artisan migrate:rollback
php artisan tinker               # REPL

# Routes (routes/web.php)
Route::get('/users', [UserController::class, 'index']);
Route::post('/users', [UserController::class, 'store']);
Route::apiResource('users', UserController::class);

# Eloquent ORM
$users = User::where('active', true)->orderBy('name')->get();
User::create(['name' => 'Ali', 'email' => 'ali@test.com']);
User::find(1)->update(['age' => 23]);
User::find(1)->delete();