preg_grep函数怎么用来过滤并匹配符合正则表达式的数组元素？详细步骤解析

gitbox 2025-06-19

preg_grep 是 PHP 中一个非常有用的函数，它能够根据正则表达式过滤和匹配数组中的元素。如果你有一个数组，并且想要过滤出符合某个正则表达式规则的元素，preg_grep 就是一个非常高效的选择。

本篇文章将详细介绍 preg_grep 函数的用法，并通过具体的示例来帮助大家更好地理解它的功能。

1. preg_grep 函数的基本语法

<span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$pattern</span></span><span>, </span><span><span class="hljs-keyword">array</span></span><span> </span><span><span class="hljs-variable">$input</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$flags</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>): </span><span><span class="hljs-keyword">array</span></span><span>
</span></span>

$pattern：这是一个正则表达式，PHP 会根据这个正则来匹配数组中的元素。
$input：需要过滤的数组。
$flags：可选的标志参数，决定了返回的数组类型。常用的标志有 PREG_GREP_INVERT 和 PREG_GREP_ARRAY.

2. preg_grep 函数的返回值

preg_grep 会返回一个新的数组，包含所有匹配正则表达式的元素。如果没有元素匹配正则表达式，则返回一个空数组。

3. 使用示例

3.1 基本用法

假设我们有一个包含若干字符串的数组，我们想要筛选出所有包含数字的字符串，可以使用 preg_grep 函数配合正则表达式来实现。

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$input</span></span><span> = [</span><span><span class="hljs-string">"apple123"</span></span><span>, </span><span><span class="hljs-string">"banana"</span></span><span>, </span><span><span class="hljs-string">"cherry45"</span></span><span>, </span><span><span class="hljs-string">"date"</span></span><span>];

</span><span><span class="hljs-variable">$pattern</span></span><span> = </span><span><span class="hljs-string">'/\d+/'</span></span><span>; </span><span><span class="hljs-comment">// 匹配包含数字的字符串</span></span><span>

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-variable">$pattern</span></span><span>, </span><span><span class="hljs-variable">$input</span></span><span>);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

输出：

<span><span>Array
(
    [</span><span><span class="hljs-meta">0</span></span><span>] =&gt; apple123
    [</span><span><span class="hljs-meta">2</span></span><span>] =&gt; cherry45
)
</span></span>

在这个例子中，preg_grep 函数返回了包含数字的两个字符串。

3.2 使用 PREG_GREP_INVERT 标志反向过滤

如果你希望获取不符合正则表达式的元素，可以使用 PREG_GREP_INVERT 标志。这样，函数会返回那些没有匹配正则表达式的元素。

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$input</span></span><span> = [</span><span><span class="hljs-string">"apple123"</span></span><span>, </span><span><span class="hljs-string">"banana"</span></span><span>, </span><span><span class="hljs-string">"cherry45"</span></span><span>, </span><span><span class="hljs-string">"date"</span></span><span>];

</span><span><span class="hljs-variable">$pattern</span></span><span> = </span><span><span class="hljs-string">'/\d+/'</span></span><span>; </span><span><span class="hljs-comment">// 匹配包含数字的字符串</span></span><span>

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-variable">$pattern</span></span><span>, </span><span><span class="hljs-variable">$input</span></span><span>, PREG_GREP_INVERT);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

输出：

<span><span>Array
(
    [</span><span><span class="hljs-meta">1</span></span><span>] =&gt; banana
    [</span><span><span class="hljs-meta">3</span></span><span>] =&gt; date
)
</span></span>

通过 PREG_GREP_INVERT，返回的是不包含数字的字符串。

3.3 使用 PREG_GREP_ARRAY 标志获取数组的键

如果你希望返回的结果保留数组的键，可以使用 PREG_GREP_ARRAY 标志。这对于需要保留原始数组索引时非常有用。

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$input</span></span><span> = [</span><span><span class="hljs-string">"apple123"</span></span><span>, </span><span><span class="hljs-string">"banana"</span></span><span>, </span><span><span class="hljs-string">"cherry45"</span></span><span>, </span><span><span class="hljs-string">"date"</span></span><span>];

</span><span><span class="hljs-variable">$pattern</span></span><span> = </span><span><span class="hljs-string">'/\d+/'</span></span><span>; </span><span><span class="hljs-comment">// 匹配包含数字的字符串</span></span><span>

</span><span><span class="hljs-variable">$result</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-variable">$pattern</span></span><span>, </span><span><span class="hljs-variable">$input</span></span><span>, PREG_GREP_ARRAY);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$result</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

输出：

<span><span>Array
(
    [</span><span><span class="hljs-meta">0</span></span><span>] =&gt; apple123
    [</span><span><span class="hljs-meta">2</span></span><span>] =&gt; cherry45
)
</span></span>

这样，返回的数组中将包含原始数组的键。

4. 进阶用法：多种正则匹配

如果你希望对数组中的元素应用多个正则规则，可以将多个正则表达式结合起来使用。

例如，我们可以先匹配所有包含数字的元素，然后再匹配长度超过 6 的字符串。

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$input</span></span><span> = [</span><span><span class="hljs-string">"apple123"</span></span><span>, </span><span><span class="hljs-string">"banana"</span></span><span>, </span><span><span class="hljs-string">"cherry45"</span></span><span>, </span><span><span class="hljs-string">"date"</span></span><span>, </span><span><span class="hljs-string">"watermelon321"</span></span><span>];

</span><span><span class="hljs-variable">$pattern</span></span><span> = </span><span><span class="hljs-string">'/\d+/'</span></span><span>; </span><span><span class="hljs-comment">// 匹配包含数字的字符串</span></span><span>

</span><span><span class="hljs-comment">// 使用 preg_grep 筛选出包含数字的元素</span></span><span>
</span><span><span class="hljs-variable">$matched</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-variable">$pattern</span></span><span>, </span><span><span class="hljs-variable">$input</span></span><span>);

</span><span><span class="hljs-comment">// 筛选出长度大于6的元素</span></span><span>
</span><span><span class="hljs-variable">$long_words</span></span><span> = </span><span><span class="hljs-title function_ invoke__">preg_grep</span></span><span>(</span><span><span class="hljs-string">'/^.{7,}$/'</span></span><span>, </span><span><span class="hljs-variable">$matched</span></span><span>);

</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$long_words</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

输出：

<span><span>Array
(
    [</span><span><span class="hljs-meta">0</span></span><span>] =&gt; apple123
    [</span><span><span class="hljs-meta">4</span></span><span>] =&gt; watermelon321
)
</span></span>

在这个例子中，先筛选出包含数字的元素，再对结果进行第二次筛选，找出那些长度大于 6 的字符串。

5. 总结

preg_grep 是一个非常强大的函数，适用于根据正则表达式来过滤数组中的元素。通过合理使用它的正则表达式和标志选项，你可以轻松实现各种复杂的匹配和过滤需求。希望本文的介绍能够帮助你更好地掌握 preg_grep 的使用方法，提升你在 PHP 编程中的效率。

preg_grep