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<!DOCTYPE html>
<html>
<body>
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<h1>正则表达式修饰符：\u</h1>
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<p>在文本 "W3School has been live since 2006" 中，有多少个数字 "9" 出现？</p>
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<p>使用 "9" 的十六进制等价形式 0039。</p>
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<?php
$txt = "W3School has been live since 2006";
$pattern = "/\u{0039}/";
echo preg_match_all($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>（每个匹配项被替换为 # 字符）</p>
​
</body>
</html>