header("location:b.php");
<form method="post" action="b.php">
<input type="submit" name="btn" value="GO TO b.php">
</from><a href="b.php">b.php</a>
<meta http-equiv="refresh" content="0; url='http://www.qq.com/'">
<input type="button" onclick='location.href=("b.php")' />
<script>location="b.php"</script>