(PHP) LogIn script Doesn't work

Question

<?php

//CONNECT TO DATABASE

$db_host="localhost";
$db_username="root";
$db_pass="";
$db_name="admin";


    @mysql_connect("$db_host","$db_username","$db_pass","$db_name")
     or die ("not connect");
     @mysql_select_db("$db_name") or die ("no database");

     echo "succesful connection";

//THEN I CHECK THE VALUES FROM MY FORM

    if($_SERVER ['REQUEST_METHOD']=='POST'){

        $username=$_POST['username'];
        $password=$_POST['password'];

        $username=htmlspecialchars($username);
        $password=htmlspecialchars($password);

//SEARCH INTO MY DATABASE TABLE

        $SQL="SELECT * FROM members WHERE`` username=$username AND  password=$password ";
        $result=mysql_query($SQL);

//BASED ON MY RESULTS I GIVE TO SESSION VARIABLE A VALUE 1 OR "" AND REDIRECT TO INDEX.PHP

        if($result){
            $num_rows=mysql_num_rows($result);
            if($num_rows>0){
                session_start();
                $_SESSION['check']="1";
                header ("Location:index.php");
            }
            else{
                session_start();
                $_SESSION['check']="";
                header ("Location:index.php");

            }
        }

    }



    ?>

Answer 1

I think you have issue in your sql query. So try this

$SQL="SELECT * FROM members WHERE `username`='".$username."' AND  `password`='".$password."' ";

Issue :

1) You are using direct $username without single quote so if username is string it will not work

2) check that special character you are using after WHERE