<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<?php
session_start();
//$_SESSION=array();
session_destroy();
exit("<script>
			alert('已退出');
			location.href='login.php';
		</script>");
?>
</body>
</html>

$_SESSION=array();
session_destroy();
两种方式之一都可以注销掉session服务器里面的数据
exit("<script>
			alert('已退出');
			location.href='login.php';
		</script>");