为WordPress后台添加返回顶部按钮

以下代码放到主题的functions.php中

//后台添加返回顶部
add_filter('update_footer', 'left_admin_footer_text',11);
 add_action('admin_enqueue_scripts', 'pluginScripts' );
function left_admin_footer_text($text) {
$text1 = '<div class="adminup">返回顶部</div>';
return $text.$text1;
}
 function pluginScripts() {
 echo '
 <script type="text/javascript" src="http://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
 <script type="text/javascript">
 $(window).scroll(function(){
 if($(window).scrollTop()>250){
 $(".adminup").show();
 }else{
 $(".adminup").hide();
 }
 });
 $(window).load(function () {
 $(".adminup").click(function(){
 $(\'html, body\').animate({scrollTop: 0}, 200);
 });
 });
 </script>
 <style>
 .adminup {
position: fixed;
display:none;
bottom: 30px;
right: 2px;
width: 38px;
background-color: #CCCC33;
color: #fff;
text-align: center;
z-index: 55;
cursor: s-resize;
}</style>
 ';
 }