PHP页面实现登录时返回本页面并弹出相应提示

输入密码在情况
$usr=$_GET['usr'];
.....
if($usr&&$pwd)
{
$sql="select usr,pwd from table where usr='$usr' limit 1";
$ok=mysql_query($sql);
if(mysql_num_rows($ok))
{
$rs=mysql_fetch_array($ok));
if($rs['pwd']==$pwd)
{ echo "