PHP Composer Quick Reference Cheat Sheet

composer init                    # Create composer.json
composer require vendor/pkg      # Add dependency
composer require --dev vendor/pkg # Dev dependency
composer install                 # Install from lock
composer update                  # Update deps
composer dump-autoload -o        # Optimize autoload
composer show                    # List packages
composer why vendor/pkg          # Why installed

// Arrays
$arr = [1, 2, 3];
array_push($arr, 4);        // Append
array_merge($a, $b);        // Merge
array_filter($arr, fn($v) => $v > 1);
array_map(fn($v) => $v * 2, $arr);
array_reduce($arr, fn($c, $v) => $c + $v, 0);
in_array($needle, $arr);
array_key_exists('k', $arr);

// String operations
str_contains($h, $n);  str_starts_with($h, $p);
str_ends_with($h, $s); strtolower($s); strtoupper($s);
substr($s, 0, 5); explode(',', $s); implode(',', $a);

// Match expression (PHP 8.0+)
$result = match($status) {
    'active' => 'User is active',
    'inactive', 'banned' => 'User cannot login',
    default => 'Unknown status',
};

// Null coalescing
$name = $input ?? 'default';
$name ??= 'default';  // Assignment

// Null-safe operator
$country = $user?->address?->country;

// Spread operator
function sum(int ...$nums): int {
    return array_sum($nums);
}
$merged = [...$arr1, ...$arr2];

// Constructor promotion (PHP 8.0+)
class User {
    public function __construct(
        public readonly int $id,
        public string $name,
        private string $email,
    ) {}
}

// Interface
interface Cacheable {
    public function getCacheKey(): string;
    public function getCacheTTL(): int;
}

// Enum (PHP 8.1+)
enum Role: string {
    case Admin = 'admin';
    case User = 'user';
    public function isAdmin(): bool {
        return $this === self::Admin;
    }
}

// File operations
$content = file_get_contents('file.txt');
file_put_contents('out.txt', $data);
$lines = file('file.txt', FILE_IGNORE_NEW_LINES);

// JSON
$json = json_encode($data, JSON_THROW_ON_ERROR);
$data = json_decode($json, true, 512, JSON_THROW_ON_ERROR);

// CSV
$fp = fopen('data.csv', 'r');
while (($row = fgetcsv($fp)) !== false) {
    process($row);
}
fclose($fp);