/**
php中的大U函数三个参数：
U('ajaxDelPic') ==> /index.php/Admin/Goods/ajaxDelPic.html
U('ajaxDelPic?id=1') ==> /index.php/Admin/Goods/ajaxDelPic/id/1.html
U('ajaxDelPic', array('id'=>1)) ==> /index.php/Admin/Goods/ajaxDelPic/id/1.html
U('ajaxDelPic', array('id'=>1), FALSE) ==> /index.php/Admin/Goods/ajaxDelPic/id/1
**/