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<body>
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<h1>正则表达式修饰符：cat|dog|fish</h1>
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<p>在文本 "We have three dogs, one fish, but no cats" 中，"cat"、"dog" 或 "fish" 出现了多少次：</p>
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<?php
$txt = "We have three dogs, one fish, but no cats";
$pattern = "/cat|dog|fish/";
echo preg_match_all($pattern, $txt);
?>  
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<p>匹配到的位置如下：</p>
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<?php
echo preg_replace($pattern, "#", $txt);
?>  
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<p>（每个匹配项都被替换为 # 字符）</p>
​
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