php中的$_GET如何获取带有“#”的参数

<?phpecho $_GET['key'];?>

<input placeholder="输入SN码" type="text" id="searchs" name="searchs"><a class="btn" onclick="searchsn();" href="javascript:;">查询</a><script>    function searchsn() {        var keys = $('#searchs').val();        if (keys == '') {            alert('请填写SN码');            return false;        }        keys = escape(keys); //对字符串进行编码，* @ - _ + . / 这几个字符除外        window.location.href = 'c.php?key=' + keys;    }</script>