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31 個實用 PHP 自訂函數大全：字串、陣列、檔案、網路、安全、圖片處理

編輯：PHP 相關知識

前言

PHP 內建函數庫雖強大，但實務開發常需針對特定業務封裝工具函數。本文精選 31 個高頻實用自訂函數，涵蓋隨機字串、郵件編碼驗證、目錄操作、JSON/XML 解析、Slug 生成、真實 IP 取得、強制下載、標籤雲、Gravatar、文字截斷、ZIP 壓縮解壓、URL 處理、縮圖、AJAX 偵測、關鍵字高亮、Feedburner 統計、密碼生成、CSS 壓縮、短網址、年齡計算、執行計時、維護模式、快取控制、序數詞綴等。

分類速查索引

字串與隨機：1-3, 13, 15, 18, 19, 31
安全與驗證：4, 11, 17, 22, 42
檔案與目錄：5, 6, 16, 17
資料解析：7, 8
Web 實用工具：9, 10, 14, 20, 21, 26, 28, 30
綜合工具：12, 23, 24, 25, 27, 29

字串與隨機

1. 可讀性隨機字串（交替子音母音）

function readable_random_string($length = 6) {
    $conso = ['b','c','d','f','g','h','j','k','l','m','n','p','r','s','t','v','w','x','y','z'];
    $vocal = ['a','e','i','o','u'];
    $password = '';
    for ($i = 0; $i < $length / 2; $i++) {
        $password .= $conso[array_rand($conso)] . $vocal[array_rand($vocal)];
    }
    return $password;
}

2. 通用隨機字串（含數字大小寫）

function generate_rand($l) {
    $c = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    $rand = '';
    for ($i = 0; $i < $l; $i++) {
        $rand .= $c[random_int(0, strlen($c) - 1)]; // PHP 7+ 用 random_int
    }
    return $rand;
}

3. 郵件地址編碼為 HTML 實體（防爬蟲）

function encode_email($email = 'info@domain.com', $linkText = 'Contact Us', $attrs = 'class="emailencoder"') {
    $email = str_replace(['@', '.'], ['@', '.'], $email);
    $linkText = str_replace(['@', '.'], ['@', '.'], $linkText);
    return '<script>document.write(\'<a href="mailto:' . $email . '" ' . $attrs . '>' . $linkText . '</a>\');</script>';
}

13. 兩字串相似度比較

similar_text($string1, $string2, $percent); // $percent 回傳相似百分比

15. 單字邊界截斷（不斷詞）

function myTruncate($string, $limit, $break = " ", $pad = "...") {
    if (strlen($string) <= $limit) return $string;
    if (false !== ($breakpoint = strpos($string, $break, $limit))) {
        if ($breakpoint < strlen($string) - 1) {
            return substr($string, 0, $breakpoint) . $pad;
        }
    }
    return $string;
}

18. URL 自動補全 https://

if (!preg_match("/^(http|ftp):/", $_POST['url'])) {
    $_POST['url'] = 'https://' . $_POST['url'];
}

19. 字串中 URL/Email 自動轉超連結

function makeClickableLinks($text) {
    $text = preg_replace('/((f|ht)tp:\/\/[^\s]+)/i', '<a href="$1">$1</a>', $text);
    $text = preg_replace('/([\s(\[{])(www\.[^\s]+)/i', '$1<a href="https://$2">$2</a>', $text);
    $text = preg_replace('/([\w\-\.]+@[\w\-\.]+\.\w+)/', '<a href="mailto:$1">$1</a>', $text);
    return $text;
}

31. 數字加英文序數詞綴 (1st, 2nd, 3rd, 4th...)

function make_ranked($rank) {
    $last = (int)substr($rank, -1);
    $seclast = (int)substr($rank, -2, 1);
    if ($last > 3 || $last == 0) $ext = 'th';
    elseif ($last == 3) $ext = 'rd';
    elseif ($last == 2) $ext = 'nd';
    else $ext = 'st';
    // 11, 12, 13 例外
    if ($seclast == 1) $ext = 'th';
    return $rank . $ext;
}

安全與驗證

4. 郵件驗證（可選檢查 MX 記錄）

function is_valid_email($email, $test_mx = false) {
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) return false;
    if ($test_mx) {
        list(, $domain) = explode('@', $email);
        return checkdnsrr($domain, 'MX');
    }
    return true;
}

11. 強制檔案下載

function force_download($file) {
    if (isset($file) && file_exists($file)) {
        header("Content-Length: " . filesize($file));
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="' . basename($file) . '"');
        readfile($file);
        exit;
    }
    echo "No file selected";
}

21. 偵測 AJAX 請求

function is_ajax() {
    return !empty($_SERVER['HTTP_X_REQUESTED_WITH']) 
        && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) === 'xmlhttprequest';
}

22. 關鍵字高亮

function highlight($string, array $words) {
    if (empty($words) || !is_string($string)) return $string;
    $pattern = '/\b(' . implode('|', array_map('preg_quote', $words)) . ')\b/i';
    return preg_replace($pattern, '<strong>$1</strong>', $string);
}

檔案與目錄

5. 列出目錄內容（可點擊連結）

function list_files($dir) {
    if (is_dir($dir) && $handle = opendir($dir)) {
        while (($file = readdir($handle)) !== false) {
            if (!in_array($file, ['.', '..', 'Thumbs.db'])) {
                echo '<a target="_blank" href="' . $dir . $file . '">' . $file . '</a><br>';
            }
        }
        closedir($handle);
    }
}

6. 遞迴刪除目錄（含內容）

function destroyDir($dir, $virtual = false) {
    $ds = DIRECTORY_SEPARATOR;
    $dir = $virtual ? realpath($dir) : $dir;
    $dir = rtrim($dir, $ds);
    if (is_dir($dir) && $handle = opendir($dir)) {
        while ($file = readdir($handle)) {
            if ($file === '.' || $file === '..') continue;
            $path = $dir . $ds . $file;
            is_dir($path) ? destroyDir($path) : unlink($path);
        }
        closedir($handle);
        return rmdir($dir);
    }
    return false;
}

16. 建立 ZIP 壓縮檔

function create_zip($files = [], $destination = '', $overwrite = false) {
    if (file_exists($destination) && !$overwrite) return false;
    $valid_files = array_filter($files, 'file_exists');
    if (!$valid_files) return false;
    $zip = new ZipArchive();
    if ($zip->open($destination, $overwrite ? ZipArchive::OVERWRITE : ZipArchive::CREATE) !== true) return false;
    foreach ($valid_files as $file) $zip->addFile($file, basename($file));
    return $zip->close() && file_exists($destination);
}

17. 解壓縮 ZIP 檔

function unzip_file($file, $destination) {
    $zip = new ZipArchive();
    if ($zip->open($file) !== true) die('Could not open archive');
    $zip->extractTo($destination);
    $zip->close();
    echo 'Archive extracted to directory';
}

資料解析

7. JSON 解析

$json = '{"id":1,"name":"foo","email":"foo@foobar.com","interest":["wordpress","php"]}';
$obj = json_decode($json);
echo $obj->name;        // foo
echo $obj->interest[1]; // php

8. XML 解析 (SimpleXML)

$xml = simplexml_load_string($xml_string);
foreach ($xml->user as $user) {
    echo $user['id'] . ' ' . $user->name . ' ' . $user->email . '<br>';
}

Web 實用工具

9. 建立部落格 Slug（友善網址）

function create_slug($string) {
    return strtolower(trim(preg_replace('/[^A-Za-z0-9-]+/', '-', $string), '-'));
}

10. 取得客戶端真實 IP（支援代理）

function getRealIpAddr() {
    if (!empty($_SERVER['HTTP_CLIENT_IP'])) return $_SERVER['HTTP_CLIENT_IP'];
    if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) return $_SERVER['HTTP_X_FORWARDED_FOR'];
    return $_SERVER['REMOTE_ADDR'];
}

14. 顯示 Gravatar 大頭貼

function show_gravatar($email, $size = 80, $default = '', $rating = 'G') {
    echo '<img src="https://www.gravatar.com/avatar/' . md5(strtolower(trim($email))) 
        . '?s=' . $size . '&d=' . urlencode($default) . '&r=' . $rating 
        . '" width="' . $size . '" height="' . $size . '" />';
}

20. 圖片縮圖（等比例縮放）

function resize_image($filename, $tmpname, $xmax, $ymax) {
    $ext = strtolower(pathinfo($filename, PATHINFO_EXTENSION));
    $create = ['jpg' => 'imagecreatefromjpeg', 'jpeg' => 'imagecreatefromjpeg', 'png' => 'imagecreatefrompng', 'gif' => 'imagecreatefromgif'];
    if (!isset($create[$ext])) return false;
    $im = $create[$ext]($tmpname);
    $x = imagesx($im); $y = imagesy($im);
    if ($x <= $xmax && $y <= $ymax) return $im;
    if ($x >= $y) { $newx = $xmax; $newy = $y * $xmax / $x; }
    else { $newy = $ymax; $newx = $x * $ymax / $y; }
    $im2 = imagecreatetruecolor($newx, $newy);
    imagecopyresampled($im2, $im, 0, 0, 0, 0, $newx, $newy, $x, $y);
    return $im2;
}

26. 取得短網址 (TinyURL)

function getTinyUrl($url) {
    return file_get_contents("https://tinyurl.com/api-create.php?url=" . urlencode($url));
}

28. 計算腳本執行時間

$time_start = microtime(true);
// ... 程式碼 ...
$time_end = microtime(true);
echo 'Script took ' . ($time_end - $time_start) . ' seconds to execute';

30. CSS 防快取（加入時間戳）

<link href="/stylesheet.css?<?php echo time(); ?>" rel="stylesheet" type="text/css" />

綜合工具

12. 標籤雲生成

function getCloud(array $data, $minFontSize = 12, $maxFontSize = 30) {
    $min = min($data); $max = max($data);
    $spread = $max - $min ?: 1;
    $html = '';
    foreach ($data as $tag => $count) {
        $size = $minFontSize + ($count - $min) * ($maxFontSize - $minFontSize) / $spread;
        $html .= '<a style="font-size:' . floor($size) . 'px" href="#" title="' . $tag . ' (' . $count . ')">' . htmlspecialchars($tag) . '</a> ';
    }
    return $html;
}

23. Feedburner 平均訂閱數

function get_average_readers($feed_id, $interval = 7) {
    $today = date('Y-m-d'); $ago = date('Y-m-d', strtotime("-$interval days"));
    $url = "https://feedburner.google.com/api/awareness/1.0/GetFeedData?uri=$feed_id&dates=$ago,$today";
    $xml = simplexml_load_string(file_get_contents($url));
    $total = 0; $count = 0;
    foreach ($xml->feed->entry as $entry) { $total += (int)$entry['circulation']; $count++; }
    return $count ? round($total / $count) : 0;
}

24. 可調強度密碼生成器

function generatePassword($length = 9, $strength = 0) {
    $vowels = 'aeuy'; $consonants = 'bdghjmnpqrstvz';
    if ($strength >= 1) $consonants .= 'BDGHJLMNPQRSTVWXZ';
    if ($strength >= 2) $vowels .= 'AEUY';
    if ($strength >= 4) $consonants .= '23456789';
    if ($strength >= 8) $vowels .= '@#$%';
    $password = ''; $alt = time() % 2;
    for ($i = 0; $i < $length; $i++) {
        $pool = $alt ? $consonants : $vowels;
        $password .= $pool[random_int(0, strlen($pool) - 1)];
        $alt = 1 - $alt;
    }
    return $password;
}

25. 合併壓縮多個 CSS 檔

header('Content-type: text/css');
ob_start(function ($buffer) {
    $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer); // 移除註解
    return str_replace(["\r\n", "\r", "\n", "\t", '  ', '   '], '', $buffer); // 移除空白
});
include('master.css'); include('typography.css'); include('grid.css');
ob_end_flush();

27. 生日計算年齡

function age($date) {
    $time = strtotime($date);
    if ($time === false) return '';
    list($year, $month, $day) = explode('-', date('Y-m-d', $time));
    $age = date('Y') - $year;
    if (date('m-d') < "$month-$day") $age--;
    return $age;
}

29. 維護模式切換

function maintenance($mode = false) {
    $script = basename($_SERVER['SCRIPT_FILENAME']);
    if ($mode && $script !== 'maintenance.php') { header('Location: /maintenance.php'); exit; }
    if (!$mode && $script === 'maintenance.php') { header('Location: /'); exit; }
}

總結

這 31 個函數涵蓋了 PHP 開發 80% 的常見需求。建議將常用者整理為專案的 helpers.php 或 Traits，配合 Composer 自動載入，建立團隊專屬工具庫。注意：部分原始代碼使用已棄用函數（ereg, split, rand），實際使用請替換為 preg_*, explode, random_int 等現代替代品。