PHP 開發必備：23 個實用代碼片段精選（簡訊、郵件、防注入、圖片處理等）

12. IP 黑名單封鎖

$deny = ['192.168.1.100', '10.0.0.5'];
if (in_array(getRealIp(), $deny)) {
    exit('Your IP is blocked.');
}

13. 強制檔案下載

function forceDownload($filePath, $fileName = null) {
    if (!file_exists($filePath)) return false;
    $fileName = $fileName ?? basename($filePath);
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . $fileName . '"');
    header('Content-Length: ' . filesize($filePath));
    readfile($filePath);
    exit;
}

14. 產生 JSON 回應

header('Content-Type: application/json');
echo json_encode(['id' => 1, 'name' => 'John', 'tags' => ['php', 'api']], JSON_UNESCAPED_UNICODE);

15. 建立 ZIP 壓縮檔

function createZip(array $files, $zipPath, $overwrite = false) {
    if (file_exists($zipPath) && !$overwrite) return false;
    $zip = new ZipArchive();
    if ($zip->open($zipPath, $overwrite ? ZipArchive::OVERWRITE : ZipArchive::CREATE) !== true) return false;
    foreach ($files as $file) if (file_exists($file)) $zip->addFile($file, basename($file));
    $zip->close();
    return file_exists($zipPath);
}

16. 解壓縮 ZIP

function unzip($zipPath, $destDir) {
    $zip = new ZipArchive();
    if ($zip->open($zipPath) !== true) return false;
    $zip->extractTo($destDir);
    $zip->close();
    return true;
}

17. 圖片等比縮放

function resizeImage($srcPath, $maxW, $maxH, $destPath) {
    list($w, $h, $type) = getimagesize($srcPath);
    if ($w <= $maxW && $h <= $maxH) return copy($srcPath, $destPath);
    $ratio = min($maxW/$w, $maxH/$h);
    $newW = (int)($w * $ratio);
    $newH = (int)($h * $ratio);
    $src = match($type) {
        IMAGETYPE_JPEG => imagecreatefromjpeg($srcPath),
        IMAGETYPE_PNG => imagecreatefrompng($srcPath),
        IMAGETYPE_GIF => imagecreatefromgif($srcPath),
        default => return false,
    };
    $dst = imagecreatetruecolor($newW, $newH);
    imagecopyresampled($dst, $src, 0, 0, 0, 0, $newW, $newH, $w, $h);
    switch ($type) {
        case IMAGETYPE_JPEG: imagejpeg($dst, $destPath, 90); break;
        case IMAGETYPE_PNG: imagepng($dst, $destPath); break;
        case IMAGETYPE_GIF: imagegif($dst, $destPath); break;
    }
    imagedestroy($src); imagedestroy($dst);
    return true;
}

18. 使用 mail() 發送 HTML 郵件

function mailHtml($to, $subject, $html) {
    $headers = "From: System <noreply@example.com>\r\n";
    $headers .= "Reply-To: noreply@example.com\r\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/html; charset=UTF-8\r\n";
    return mail($to, $subject, $html, $headers);
}

19. 秒數轉人類可讀時間

function secondsToHuman($secs) {
    $units = [['year', 31536000], ['month', 2592000], ['week', 604800], ['day', 86400], ['hour', 3600], ['minute', 60], ['second', 1]];
    $parts = [];
    foreach ($units as [$name, $val]) {
        if ($secs >= $val) {
            $count = (int)($secs / $val);
            $parts[] = "$count $name" . ($count > 1 ? 's' : '');
            $secs %= $val;
        }
    }
    return implode(', ', $parts) ?: '0 seconds';
}

20. MySQL 連線（PDO 版）

$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8mb4', 'user', 'pass', [
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES => false,
]);

21. 列出目錄檔案

function listFiles($dir) {
    if (!is_dir($dir)) return [];
    return array_diff(scandir($dir), ['.', '..']);
}

22. 偵測瀏覽器語言

function detectLanguage(array $supported = ['en','zh-TW','ja'], $default = 'en') {
    if (empty($_SERVER['HTTP_ACCEPT_LANGUAGE'])) return $default;
    foreach (explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']) as $lang) {
        $code = strtolower(substr($lang, 0, 2));
        if (in_array($code, $supported)) return $code;
    }
    return $default;
}

23. 讀取 CSV 檔案

function readCsv($path) {
    $rows = [];
    if (($h = fopen($path, 'r')) !== false) {
        while (($row = fgetcsv($h, 1024)) !== false) $rows[] = $row;
        fclose($h);
    }
    return $rows;
}

使用建議

• 將常用函式集中放入 helpers.php 並用 Composer files 自動載入。
• 涉及外部 API（簡訊、郵件、IP 查詢）請務必加入錯誤處理、重試與日誌。
• 資料庫操作一律使用 Prepared Statements，切勿拼接 SQL 字串。

這 23 個片段覆蓋了 PHP 專案 80% 的常見需求，建議收藏並依專案慣用風格微調。