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preg_replace 正则表达式语法入门：从零开始学会正则替换技巧

gitbox 2025-09-17

在 PHP 里，preg_replace() 是处理文本最趁手的“瑞士军刀”。它基于 PCRE（Perl Compatible Regular Expressions），既能做简单的查找替换，也能完成结构化重写、清洗数据、批量改名等复杂任务。本文将从零开始，围绕 preg_replace() 的函数签名、正则语法、常见场景与避坑要点，帮你迅速掌握正则替换的核心技巧。

1. preg_replace() 基本用法

函数签名：

<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：正则表达式（可为数组，表示多规则）

  • $replacement：替换内容（可为数组，与 pattern 一一对应）

  • $subject：待处理的字符串（或字符串数组）

  • $limit：替换次数上限（默认 -1 表示不限制）

  • $count：输出参数，返回实际替换次数

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：? 让前面的 u 可选；i 修饰符忽略大小写。

2. 分隔符与修饰符

2.1 分隔符（delimiters）

常见分隔符有 / # ~ % { } ( ) 等。选择不与模式冲突的分隔符最省心：

<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>

当模式里有大量 / 时，改用 # 能避免大量转义。

2.2 常用修饰符（modifiers）

  • i：忽略大小写

  • m：多行模式（^、$ 会匹配每一行的行首/行尾）

  • s：单行模式（. 也匹配换行）

  • u：按 UTF-8 处理（中文/emoji 场景强烈推荐）

  • x：忽略模式中的空白与注释（可读性更好）

  • U：懒惰量词反转（将量词默认从贪婪变为惰性）

示例（多行 + 单行）：

<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. 元字符与量词快速上手

  • 字符类：[abc]、[^abc]、\d 数字、\w 单词字符、\s 空白

  • 位置锚点：^ 行首，$ 行尾，\b 单词边界

  • 量词：*(0+), +(1+), ?(0/1), {m,n}(范围)

  • 贪婪/惰性：+ 是贪婪，+? 是惰性（尽可能少匹配）

示例（邮箱掩码）：

<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>

使用前后查找 (?<=...)、(?=...) 精准定位替换范围，避免捕获多余字符。

4. 捕获分组与反向引用

  • 捕获分组：(...) 会把匹配内容保存到 $1, $2, ...（在替换字符串中使用）

  • 非捕获分组：(?:...) 仅分组不保存，性能更好

示例（姓名格式化：张三-李四 → 张三 & 李四）：

<span><span><span class="hljs-variable">$name</span></span><span> = </span><span><span class="hljs-string">'张三-李四'</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">preg_replace</span></span><span>(</span><span><span class="hljs-string">'/^(\S+)\s*-\s*(\S+)$/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">// 张三 &amp; 李四</span></span><span>
</span></span>

示例（URL 标准化：HTTP://EXAMPLE.COM/Path → 小写域名）：

<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>

?? 老代码可能出现 /e 修饰符（已废弃），不要使用。请改用 回调（见下一节）。

5. 用回调做“智能替换”：preg_replace_callback()

当替换值需要计算（如大小写转换、动态编号、条件判断）时，用回调更安全：

<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">// $m[0] 是整个匹配，$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>

还有一个适合处理大量数据的姐妹函数：preg_replace_callback_array()，可一次注册多条规则与其回调：

<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. 多规则批量替换

$pattern 和 $replacement 都支持数组。如果替换值不是一一对应，则会用同一个替换值应用到每个模式：

<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/中文与边界问题

默认建议加 u 修饰符，避免把多字节字符拆坏。

  • 中文分词边界可用 \b？不可靠。\b 是“单词边界”，针对 ASCII 单词字符；处理中文边界请用明确的字符类或前后查找。

示例（给中文与数字之间加空格）：

<span><span><span class="hljs-variable">$str</span></span><span> = </span><span><span class="hljs-string">"版本2已发布在2025年8月25日"</span></span><span>;
</span><span><span class="hljs-variable">$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 已发布在 2025 年 8 月 25 日</span></span><span>
</span></span>

\x{4e00}-\x{9fa5} 是常用汉字区间，记得加 u。

8. 常见替换场景实战

8.1 HTML 清洗（小心别写成“解析 HTML”的锤子）

目标：去掉所有标签，仅保留纯文本。

<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>

简单清洗 OK；复杂 HTML 结构请用 DOM 才健壮。

8.2 电话/卡号脱敏

<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 批量变量占位替换（花括号语法）

<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 图片转 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 规范化空白与标点

<span><span><span class="hljs-variable">$text</span></span><span> = </span><span><span class="hljs-string">"Hello，world!   PHP\tis\ngreat."</span></span><span>;
</span><span><span class="hljs-comment">// 把非换行的连续空白压成一个空格</span></span><span>
</span><span><span class="hljs-variable">$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">$text</span></span><span>);
</span><span><span class="hljs-comment">// 替换中文逗号为英文逗号后加空格</span></span><span>
</span><span><span class="hljs-variable">$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 提取并重组（日志字段重排）

<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. 性能与可靠性建议

  1. 优先具体，后泛化：字符类尽量窄，避免 .* 滥用。必要时改用惰性量词或前后查找。

  2. 避免灾难性回溯：模式中 (.+)+、(.*){m,} 这类结构极易爆栈；能明确边界就别用“贪吃蛇”。

  3. 使用 u 修饰符：文本包含多字节字符（中文/emoji）时必须加上，否则可能破坏字符。

  4. 回调代替 /e：任何需要计算的替换都用 preg_replace_callback()，更安全。

  5. 控制 $limit：当你只想替换第一个匹配时，把 $limit 设为 1。

  6. 统计与测试：利用 $count 收集替换次数；为关键模式写单元测试，覆盖边界用例。

  7. 预编译/缓存：PHP 内部对 PCRE 有一定缓存；但在高频路径上，尽量避免在循环中构造可变模式。

10. 纠错与调试

  • 最小化重现：把长模式拆小，逐段验证。

  • 可读性：用 x 修饰符写“带注释”的模式：

<span><span><span class="hljs-variable">$pattern</span></span><span> = <span class="hljs-string">'/
    ^\s*              # 开头允许空白
    (?P&lt;key&gt;\w+)      # 键
    \s*=\s*
    (?P&lt;val&gt;.+?)      # 值（惰性）
    \s*$
/x'</span>;
</span></span>

  • 转义意识：在 PHP 字符串里要双重考虑转义（例如 "\d" 与 \\d 的区别）。

11. 常用“秘籍”清单

  • 只替换第一个匹配：preg_replace($p, $r, $s, 1, $count);

  • 安全移除脚本标签：preg_replace('#<script\b[^>]*>.*?</script>#is', '', $html);

  • URL 中的查询参数重命名：匹配 ([?&])old=([^&#]*) → $1new=$2

  • 千分位插入逗号（简单数值）：preg_replace('/\B(?=(\d{3})+(?!\d))/', ',', $n);

  • 多余空行压缩：preg_replace('/(\R)\s*(\R)/', "$1$2", $text);

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

  • 驼峰转下划线：preg_replace('/(?<!^)[A-Z]/', '_$0', $camel);

12. 综合示例：日志脱敏 + 结构化输出

<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) 基础脱敏：手机号中间四位打星、邮箱用户名只留首字符</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) 结构化重写：转成 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>

结语

preg_replace() 的威力在于“精确描述你要找的模式，并把它改写成你需要的样子”。把握分隔符与修饰符、善用捕获分组与前后查找、在需要计算时用回调，你就能在日常开发中游刃有余地完成从清洗到重写的各种文本任务。多写小例子、多做边界测试，正则会从“黑魔法”变成顺手的日常工具。

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