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preg_replace 正則表達式語法入門：從零開始學會正則替換技巧

gitbox 2025-09-17

在PHP 裡， preg_replace()是處理文本最趁手的“瑞士軍刀”。它基於PCRE（Perl Compatible Regular Expressions），既能做簡單的查找替換，也能完成結構化重寫、清洗數據、批量改名等複雜任務。本文將從零開始，圍繞preg_replace()的函數簽名、正則語法、常見場景與避坑要點，幫你迅速掌握正則替換的核心技巧。

1. preg_replace()基本用法

函數簽名：

 <span><span><span class="hljs-keyword">mixed</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(
    </span><span><span class="hljs-keyword">string</span></span><span>|</span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-variable">$pattern</span></span><span>,
    </span><span><span class="hljs-keyword">string</span></span><span>|</span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-variable">$replacement</span></span><span>,
    </span><span><span class="hljs-keyword">string</span></span><span>|</span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-variable">$subject</span></span><span>,
    </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$limit</span></span><span> = -</span><span><span class="hljs-number">1</span></span><span>,
    </span><span><span class="hljs-keyword">int</span></span><span> &amp;</span><span><span class="hljs-variable">$count</span></span><span> = </span><span><span class="hljs-literal">null</span></span><span>
)
</span></span>

  • $pattern ：正則表達式（可為數組，表示多規則）

  • $replacement ：替換內容（可為數組，與pattern 一一對應）

  • $subject ：待處理的字符串（或字符串數組）

  • $limit ：替換次數上限（默認-1 表示不限制）

  • $count ：輸出參數，返回實際替換次數

最小示例：

 <span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-string">"Color or Colour? I like the color blue."</span></span><span>;
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/colou?r/i'</span></span><span>, </span><span><span class="hljs-string">'color'</span></span><span>, </span><span><span class="hljs-variable">$text</span></span><span>, -</span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-variable">$count</span></span><span>);

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$result</span></span><span>; </span><span><span class="hljs-comment">// Color or color? I like the color blue.</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> PHP_EOL . </span><span><span class="hljs-string">"Replaced: <span class="hljs-subst">$count</span></span></span><span>"; </span><span><span class="hljs-comment">// Replaced: 2</span></span><span>
</span></span>

/colou?r/i ： ?讓前面的u可選； i修飾符忽略大小寫。

2. 分隔符與修飾符

2.1 分隔符（delimiters）

常見分隔符有/ # ~ % { } ( )等。選擇不與模式衝突的分隔符最省心：

 <span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'#https?://[^\s]+#'</span></span><span>, </span><span><span class="hljs-string">'[link]'</span></span><span>, </span><span><span class="hljs-variable">$text</span></span><span>);
</span></span>

當模式裡有大量/時，改用#能避免大量轉義。

2.2 常用修飾符（modifiers）

  • i ：忽略大小寫

  • m ：多行模式（ ^ 、 $會匹配每一行的行首/行尾）

  • s ：單行模式（ .也匹配換行）

  • u ：按UTF-8 處理（中文/emoji 場景強烈推薦）

  • x ：忽略模式中的空白與註釋（可讀性更好）

  • U ：懶惰量詞反轉（將量詞默認從貪婪變為惰性）

示例（多行+ 單行）：

 <span><span><span class="hljs-variable">$log</span></span><span> = </span><span><span class="hljs-string">"ID:42\nPayload:\n{\n  \"a\":1\n}\nEnd"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/^Payload:(.*)End$/ims'</span></span><span>, </span><span><span class="hljs-string">'[DATA HIDDEN]'</span></span><span>, </span><span><span class="hljs-variable">$log</span></span><span>);
</span></span>

3. 元字符與量詞快速上手

  • 字符類： [abc] 、 [^abc] 、 \d數字、 \w單詞字符、 \s空白

  • 位置錨點： ^行首， $行尾， \b單詞邊界

  • 量詞： * (0+), + (1+), ? (0/1), {m,n} (範圍)

  • 貪婪/惰性： +是貪婪， +?是惰性（盡可能少匹配）

示例（郵箱掩碼）：

 <span><span><span class="hljs-variable">$email</span></span><span> = </span><span><span class="hljs-string">'[email protected]'</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(?&lt;=.).+?(?=@)/'</span></span><span>, </span><span><span class="hljs-string">'***'</span></span><span>, </span><span><span class="hljs-variable">$email</span></span><span>);
</span><span><span class="hljs-comment">// a***@example.com</span></span><span>
</span></span>

使用前後查找(?<=...) 、 (?=...)精准定位替換範圍，避免捕獲多餘字符。

4. 捕獲分組與反向引用

  • 捕獲分組： (...)會把匹配內容保存到$1, $2, ... （在替換字符串中使用）

  • 非捕獲分組： (?:...)僅分組不保存，性能更好

示例（姓名格式化：張三-李四→張三& 李四）：

 <span><span><span class="hljs-variable">$name</span></span><span> = </span><span><span class="hljs-string">'張三-李四'</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/^(\S+)\s*-\s*(\S+)$/u'</span></span><span>, </span><span><span class="hljs-string">'$1 &amp; $2'</span></span><span>, </span><span><span class="hljs-variable">$name</span></span><span>);
</span><span><span class="hljs-comment">// 張三 &amp; 李四</span></span><span>
</span></span>

示例（URL 標準化： HTTP://EXAMPLE.COM/Path → 小寫域名）：

 <span><span><span class="hljs-variable">$url</span></span><span> = </span><span><span class="hljs-string">'HTTP://EXAMPLE.COM/Path'</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/^(https?):\/\/([^\/]+)/ie'</span></span><span>, </span><span><span class="hljs-string">"'<span class="hljs-subst">$1</span></span></span><span>://'.strtolower('</span><span><span class="hljs-subst">$2</span></span><span>')", </span><span><span class="hljs-variable">$url</span></span><span>);
</span></span>

?? 老代碼可能出現/e修飾符（已廢棄），不要使用。請改用回調（見下一節）。

5. 用回調做“智能替換”： preg_replace_callback()

當替換值需要計算（如大小寫轉換、動態編號、條件判斷）時，用回調更安全：

 <span><span><span class="hljs-variable">$input</span></span><span> = </span><span><span class="hljs-string">"HTTP://EXAMPLE.COM/Path and http://MiXeD.com/Another"</span></span><span>;
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace_callback</span></span><span>(
    </span><span><span class="hljs-string">'#\bhttps?://([^/\s]+)#i'</span></span><span>,
    function (</span><span><span class="hljs-variable">$m</span></span><span>) {
        </span><span><span class="hljs-comment">// $m[0] 是整個匹配，$m[1] 是域名</span></span><span>
        </span><span><span class="hljs-variable">$scheme</span></span><span> = </span><span><span class="hljs-title function_ invoke__">stripos</span></span><span>(</span><span><span class="hljs-variable">$m</span></span><span>[</span><span><span class="hljs-number">0</span></span><span>], </span><span><span class="hljs-string">'https://'</span></span><span>) === </span><span><span class="hljs-number">0</span></span><span> ? </span><span><span class="hljs-string">'https://'</span></span><span> : </span><span><span class="hljs-string">'http://'</span></span><span>;
        </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$scheme</span></span><span> . </span><span><span class="hljs-title function_ invoke__">strtolower</span></span><span>(</span><span><span class="hljs-variable">$m</span></span><span>[</span><span><span class="hljs-number">1</span></span><span>]);
    },
    </span><span><span class="hljs-variable">$input</span></span><span>
);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$result</span></span><span>;
</span><span><span class="hljs-comment">// http://example.com/Path and http://mixed.com/Another</span></span><span>
</span></span>

還有一個適合處理大量數據的姐妹函數： preg_replace_callback_array() ，可一次註冊多條規則與其回調：

 <span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-string">"Price: 19.99 USD, Date: 2025-08-25"</span></span><span>;
</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace_callback_array</span></span><span>([
    </span><span><span class="hljs-string">'/\b(\d+(?:\.\d{2})?)\s*USD\b/'</span></span><span> =&gt; fn(</span><span><span class="hljs-variable">$m</span></span><span>) =&gt; </span><span><span class="hljs-string">'$'</span></span><span> . </span><span><span class="hljs-variable">$m</span></span><span>[</span><span><span class="hljs-number">1</span></span><span>],
    </span><span><span class="hljs-string">'/\b(\d{4})-(\d{2})-(\d{2})\b/'</span></span><span>  =&gt; </span><span><span class="hljs-function"><span class="hljs-keyword">fn</span></span></span><span>(</span><span><span class="hljs-params"><span class="hljs-variable">$m</span></span></span><span>) =&gt; </span><span><span class="hljs-string">"<span class="hljs-subst">{$m[2]}</span></span></span><span>/</span><span><span class="hljs-subst">{$m[3]}</span></span><span>/</span><span><span class="hljs-subst">{$m[1]}</span></span><span>",
], </span><span><span class="hljs-variable">$text</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$result</span></span><span>; </span><span><span class="hljs-comment">// Price: $19.99, Date: 08/25/2025</span></span><span>
</span></span>

6. 多規則批量替換

$pattern和$replacement都支持數組。如果替換值不是一一對應，則會用同一個替換值應用到每個模式：

 <span><span><span class="hljs-variable">$input</span></span><span> = </span><span><span class="hljs-string">"foo 123 bar 456 baz"</span></span><span>;
</span><span><span class="hljs-variable">$patterns</span></span><span> = [</span><span><span class="hljs-string">'/\bfoo\b/'</span></span><span>, </span><span><span class="hljs-string">'/\d+/'</span></span><span>, </span><span><span class="hljs-string">'/\bbaz\b/'</span></span><span>];
</span><span><span class="hljs-variable">$replacements</span></span><span> = [</span><span><span class="hljs-string">'FOO'</span></span><span>, </span><span><span class="hljs-string">'[NUM]'</span></span><span>, </span><span><span class="hljs-string">'BAZ'</span></span><span>];
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-variable">$patterns</span></span><span>, </span><span><span class="hljs-variable">$replacements</span></span><span>, </span><span><span class="hljs-variable">$input</span></span><span>);
</span><span><span class="hljs-comment">// FOO [NUM] bar [NUM] BAZ</span></span><span>
</span></span>

7. Unicode/中文與邊界問題

默認建議加u修飾符，避免把多字節字符拆壞。

  • 中文分詞邊界可用\b ？不可靠。 \b是“單詞邊界”，針對ASCII 單詞字符；處理中文邊界請用明確的字符類或前後查找。

示例（給中文與數字之間加空格）：

 <span><span><span class="hljs-variable">$str</span></span><span> = </span><span><span class="hljs-string">"版本2已發佈在2025年8月25天"</span></span><span>;
</span><span><span class="hljs-variable">$str</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(?&lt;=[\x{4e00}-\x{9fa5}])(?=\d)/u'</span></span><span>, </span><span><span class="hljs-string">' '</span></span><span>, </span><span><span class="hljs-variable">$str</span></span><span>);
</span><span><span class="hljs-variable">$str</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(?&lt;=\d)(?=[\x{4e00}-\x{9fa5}])/u'</span></span><span>, </span><span><span class="hljs-string">' '</span></span><span>, </span><span><span class="hljs-variable">$str</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$str</span></span><span>; </span><span><span class="hljs-comment">// 版本 2 已發佈在 2025 年 8 月 25 天</span></span><span>
</span></span>

\x{4e00}-\x{9fa5}是常用漢字區間，記得加u 。

8. 常見替換場景實戰

8.1 HTML 清洗（小心別寫成“解析HTML”的錘子）

目標：去掉所有標籤，僅保留純文本。

 <span><span><span class="hljs-variable">$html</span></span><span> = </span><span><span class="hljs-string">"&lt;p&gt;Hello &lt;strong&gt;world&lt;/strong&gt; &amp;copy; 2025&lt;/p&gt;"</span></span><span>;
</span><span><span class="hljs-variable">$plain</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/&lt;[^&gt;]+&gt;/'</span></span><span>, </span><span><span class="hljs-string">''</span></span><span>, </span><span><span class="hljs-variable">$html</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$plain</span></span><span>; </span><span><span class="hljs-comment">// Hello world ? 2025</span></span><span>
</span></span>

簡單清洗OK；複雜HTML 結構請用DOM 才健壯。

8.2 電話/卡號脫敏

<span><span><span class="hljs-variable">$phone</span></span><span> = </span><span><span class="hljs-string">"13812345678"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(\d{3})\d{4}(\d{4})/'</span></span><span>, </span><span><span class="hljs-string">'$1****$2'</span></span><span>, </span><span><span class="hljs-variable">$phone</span></span><span>);
</span><span><span class="hljs-comment">// 138****5678</span></span><span>
</span></span>

8.3 批量變量佔位替換（花括號語法）

 <span><span><span class="hljs-variable">$template</span></span><span> = </span><span><span class="hljs-string">"Hi {name}, your order {id} is {status}."</span></span><span>;
</span><span><span class="hljs-variable">$data</span></span><span> = [</span><span><span class="hljs-string">'name'</span></span><span> =&gt; </span><span><span class="hljs-string">'Alice'</span></span><span>, </span><span><span class="hljs-string">'id'</span></span><span> =&gt; </span><span><span class="hljs-number">42</span></span><span>, </span><span><span class="hljs-string">'status'</span></span><span> =&gt; </span><span><span class="hljs-string">'shipped'</span></span><span>];

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace_callback</span></span><span>(</span><span><span class="hljs-string">'/\{(\w+)\}/'</span></span><span>, function(</span><span><span class="hljs-variable">$m</span></span><span>) </span><span><span class="hljs-keyword">use</span></span><span> ($</span><span><span class="hljs-title">data</span></span><span>) {
    </span><span><span class="hljs-title">return</span></span><span> $</span><span><span class="hljs-title">data</span></span><span>[$</span><span><span class="hljs-title">m</span></span><span>[1]] ?? $</span><span><span class="hljs-title">m</span></span><span>[0];
}, </span><span><span class="hljs-variable">$template</span></span><span>);
</span><span><span class="hljs-comment">// Hi Alice, your order 42 is shipped.</span></span><span>
</span></span>

8.4 Markdown 圖片轉HTML <img>

 <span><span><span class="hljs-variable">$md</span></span><span> = </span><span><span class="hljs-string">'![alt text](/img/logo.png "Title")'</span></span><span>;
</span><span><span class="hljs-variable">$img</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(
    </span><span><span class="hljs-string">'/!\[([^\]]*)\]\((\S+)(?:\s+"([^"]*)")?\)/'</span></span><span>,
    </span><span><span class="hljs-string">'&lt;img src="$2" alt="$1" title="$3"&gt;'</span></span><span>,
    </span><span><span class="hljs-variable">$md</span></span><span>
);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$img</span></span><span>;
</span><span><span class="hljs-comment">// &lt;img src="/img/logo.png" alt="alt text" title="Title"&gt;</span></span><span>
</span></span>

8.5 規範化空白與標點

<span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-string">"Hello，world!   PHP\tis\ngreat."</span></span><span>;
</span><span><span class="hljs-comment">// 把非換行的連續空白壓成一個空格</span></span><span>
</span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/[^\S\r\n]+/'</span></span><span>, </span><span><span class="hljs-string">' '</span></span><span>, </span><span><span class="hljs-variable">$text</span></span><span>);
</span><span><span class="hljs-comment">// 替換中文逗號為英文逗號後加空格</span></span><span>
</span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/，/u'</span></span><span>, </span><span><span class="hljs-string">', '</span></span><span>, </span><span><span class="hljs-variable">$text</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$text</span></span><span>; </span><span><span class="hljs-comment">// Hello, world! PHP is great.</span></span><span>
</span></span>

8.6 提取並重組（日誌字段重排）

 <span><span><span class="hljs-variable">$line</span></span><span> = </span><span><span class="hljs-string">'2025-08-25 14:03:22 [INFO] user=alice ip=203.0.113.9'</span></span><span>;
</span><span><span class="hljs-variable">$fmt</span></span><span>  = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(
    </span><span><span class="hljs-string">'/^(\d{4}-\d{2}-\d{2}) (\d{2}:\d{2}:\d{2}) \[(\w+)\] user=(\w+) ip=([\d.]+)$/'</span></span><span>,
    </span><span><span class="hljs-string">'[$3][$1T$2Z] $4@$5'</span></span><span>,
    </span><span><span class="hljs-variable">$line</span></span><span>
);
</span><span><span class="hljs-comment">// [INFO][2025-08-25T14:03:22Z] [email protected]</span></span><span>
</span></span>

9. 性能與可靠性建議

  1. 優先具體，後泛化：字符類盡量窄，避免.*濫用。必要時改用惰性量詞或前後查找。

  2. 避免災難性回溯：模式中(.+)+ 、 (.*){m,}這類結構極易爆棧；能明確邊界就別用“貪吃蛇”。

  3. 使用u修飾符：文本包含多字節字符（中文/emoji）時必須加上，否則可能破壞字符。

  4. 回調代替/e ：任何需要計算的替換都用preg_replace_callback() ，更安全。

  5. 控制$limit ：當你只想替換第一個匹配時，把$limit設為1 。

  6. 統計與測試：利用$count收集替換次數；為關鍵模式寫單元測試，覆蓋邊界用例。

  7. 預編譯/緩存：PHP 內部對PCRE 有一定緩存；但在高頻路徑上，盡量避免在循環中構造可變模式。

10. 糾錯與調試

  • 最小化重現：把長模式拆小，逐段驗證。

  • 可讀性：用x修飾符寫“帶註釋”的模式：

 <span><span><span class="hljs-variable">$pattern</span></span><span> = <span class="hljs-string">'/
    ^\s*              # 開頭允許空白
    (?P&lt;key&gt;\w+)      # 鍵
    \s*=\s*
    (?P&lt;val&gt;.+?)      # 值（惰性）
    \s*$
/x'</span>;
</span></span>

  • 轉義意識：在PHP 字符串裡要雙重考慮轉義（例如"\d"與\\d的區別）。

11. 常用“秘籍”清單

  • 只替換第一個匹配： preg_replace($p, $r, $s, 1, $count);

  • 安全移除腳本標籤： preg_replace('#<script\b[^>]*>.*?</script>#is', '', $html);

  • URL 中的查詢參數重命名：匹配([?&])old=([^&#]*) → $1new=$2

  • 千分位插入逗號（簡單數值）： preg_replace('/\B(?=(\d{3})+(?!\d))/', ',', $n);

  • 多餘空行壓縮： preg_replace('/(\R)\s*(\R)/', "$1$2", $text);

  • 去除不可見字符： preg_replace('/[\x00-\x1F\x7F]/', '', $s);

  • 駝峰轉下劃線： preg_replace('/(?<!^)[AZ]/', '_$0', $camel);

12. 綜合示例：日誌脫敏+ 結構化輸出

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$log</span></span><span> = <span class="hljs-string">&lt;&lt;&lt;LOG
[2025-08-25 10:00:01] user=john phone=13812345678 [email protected]
[2025-08-25 10:05:09] user=林 phone=13987654321 [email protected]
LOG</span>;

</span><span><span class="hljs-comment">// 1) 基礎脫敏：手機號中間四位打星、郵箱用戶名只留首字符</span></span><span>
</span><span><span class="hljs-variable">$log</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(\b1\d{2})\d{4}(\d{4}\b)/'</span></span><span>, </span><span><span class="hljs-string">'$1****$2'</span></span><span>, </span><span><span class="hljs-variable">$log</span></span><span>);
</span><span><span class="hljs-variable">$log</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/(?&lt;=\b)[A-Za-z0-9._%+-](?:[A-Za-z0-9._%+-]?)+(?=@)/'</span></span><span>, </span><span><span class="hljs-string">'*'</span></span><span>, </span><span><span class="hljs-variable">$log</span></span><span>);

</span><span><span class="hljs-comment">// 2) 結構化重寫：轉成 CSV 行</span></span><span>
</span><span><span class="hljs-variable">$csv</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(
    </span><span><span class="hljs-string">'/^\[(\d{4}-\d{2}-\d{2}) (\d{2}:\d{2}:\d{2})\]\s+user=([^\s]+)\s+phone=([^\s]+)\s+email=([^\s]+)$/mu'</span></span><span>,
    </span><span><span class="hljs-string">'$1,$2,$3,$4,$5'</span></span><span>,
    </span><span><span class="hljs-variable">$log</span></span><span>
);

</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-variable">$csv</span></span><span>;
<span class="hljs-comment">/*
2025-08-25,10:00:01,john,138****5678,j*</span></span><span><span class="hljs-doctag">@example</span></span><span>.com
2025-08-25,10:05:09,林,139****4321,l*</span><span><span class="hljs-doctag">@example</span></span><span>.cn
*/
</span></span>

結語

preg_replace()的威力在於“精確描述你要找的模式，並把它改寫成你需要的樣子”。把握分隔符與修飾符、善用捕獲分組與前後查找、在需要計算時用回調，你就能在日常開發中游刃有餘地完成從清洗到重寫的各種文本任務。多寫小例子、多做邊界測試，正則會從“黑魔法”變成順手的日常工具。

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