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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>PHP 字符串 实例 - 自学教程(runoops.com)</title>
</head>
<body>
<?php
$x = "Hello world!";
echo $x;
echo "<br>";
$x = 'Hello world!';
?>
</body>
</html>