PHP 新手必會經典代碼片段：迴圈、函式、表單、陣列、字串、日期時間實戰

6. 日期時間現代化操作 (DateTime 類別)

<?php
// 建立
$now = new DateTime('now', new DateTimeZone('Asia/Taipei'));
$specific = DateTime::createFromFormat('Y-m-d H:i:s', '2024-01-15 14:30:00');

// 格式化
echo $now->format('Y-m-d H:i:s'); // 2024-01-15 14:30:00

// 運算
$now->modify('+1 week');
$now->add(new DateInterval('P3D')); // 加 3 天
$diff = $now->diff($specific); // DateInterval 物件

// 比較
if ($now > $specific) { /* ... */ }

// 時區轉換
$utc = clone $now;
$utc->setTimezone(new DateTimeZone('UTC'));
?>

7. 檔案上傳安全處理

<?php
function handleUpload(array $file, string $uploadDir, array $allowedMimes = ['image/jpeg', 'image/png', 'image/gif']): ?string {
    if ($file['error'] !== UPLOAD_ERR_OK) return null;
    if (!in_array($file['type'], $allowedMimes, true)) return null;
    if ($file['size'] > 5 * 1024 * 1024) return null; // 5MB
    
    $ext = pathinfo($file['name'], PATHINFO_EXTENSION);
    $filename = bin2hex(random_bytes(16)) . '.' . $ext;
    $destination = $uploadDir . '/' . $filename;
    
    if (move_uploaded_file($file['tmp_name'], $destination)) {
        return $filename;
    }
    return null;
}
?>

8. JSON API 回應標準化

<?php
function jsonResponse(array $data = [], int $status = 200, string $message = ''): never {
    http_response_code($status);
    header('Content-Type: application/json; charset=UTF-8');
    echo json_encode([
        'success' => $status < 400,
        'message' => $message,
        'data' => $data,
        'timestamp' => time(),
    ], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
    exit;
}

// 用法
jsonResponse(['user' => $user], 200, '登入成功');
jsonResponse([], 422, '驗證失敗');
?>

9. 簡易快取封裝 (檔案/Redis 切換)

<?php
interface CacheDriver {
    public function get(string $key);
    public function set(string $key, $value, int $ttl): bool;
    public function delete(string $key): bool;
}

class FileCache implements CacheDriver {
    private string $dir;
    public function __construct(string $dir) { $this->dir = $dir; }
    public function get(string $key) {
        $file = $this->dir . '/' . md5($key) . '.cache';
        if (!is_file($file) || time() - filemtime($file) > 3600) return null;
        return unserialize(file_get_contents($file));
    }
    public function set(string $key, $value, int $ttl): bool {
        return file_put_contents($this->dir . '/' . md5($key) . '.cache', serialize($value)) !== false;
    }
    public function delete(string $key): bool {
        return @unlink($this->dir . '/' . md5($key) . '.cache');
    }
}
?>

10. 命令列腳本標準結構

<?php
#!/usr/bin/env php
<?php
// cli.php
if (php_sapi_name() !== 'cli') { die('CLI only'); }

$args = $argv;
array_shift($args); // 移除腳本名稱

$commands = [
    'migrate' => fn() => migrateDatabase(),
    'seed' => fn() => seedData(),
    'clean' => fn() => cleanCache(),
];

$cmd = $args[0] ?? 'help';
if (isset($commands[$cmd])) {
    $commands[$cmd]();
} else {
    echo "Usage: php cli.php [migrate|seed|clean]\n";
}
?>

內化這些模式，日常開發事半功倍，程式碼品質穩步提升。