<!DOCTYPE html>
<html>
<body>
<?php
echo "W 将输出: " . strpbrk("Hello world!","W");
echo "<br>";
echo "w 将输出: " . strpbrk("Hello world!","w");
?>
<p>此函数区分大小写（"W" 和 "w" 不会输出相同的结果）。</p>
</body>
</html>