PHP user password modification code

 @session_start();
 require_once("../inc/ring_admin.php");
 require_once("../../inc/connect.php");
 require_once ("../../admin/inc/function.php");
 ring_login();
 $pwd = get_value('pwd','post');
 $pwd2 = get_value('pwd2','post ');
 $pwd3 = get_value('pwd3','post');
 $sql = "select * from gx_member where m_pwd='".md5($pwd)."' and m_name='".$_SESSION[ 'uid']."'";

 if( $pwd2!=$pwd3 || strlen( $pwd2)<6 || strlen( $pwd2)>12 ){
 alert('Two input new The password is incorrect, please re-enter!','');
 }else{
 if(mysql_num_rows( mysql_query($sql) ) ){
 $sql="Update gx_member set m_pwd='".md5($pwd2). "' where m_name='".$_SESSION['uid']."'";
 mysql_query($sql) or die(mysql_error());
 alert('Password changed successfully!','');
 } else{
 alert('The old password is incorrect, please re-enter!','');
 }
 }
?>