mysql select with and not working properly

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PHP

MySQL

I've been battling with this for a good 5 hrs now my login script is now returning nothing.
At first it was allowing people with wrong details to Login; I made a few changes and it started denying all users, even the ones with correct login details. I removed my password condition and it retrieved the user correctly. I also then again removed the username condition and replaced it with the password condition and it retrieved all users with the same password, but when I have both conditions it returns `null`, wrong or right credentials...

    <?php
  include( '../config.php' );

  session_start();
  if( isset( $_POST['login'] ) ) {
    $username = $_POST['username'];
    $password = mysql_real_escape_string(stripslashes($_POST['password']));
    $salt = "ghvhgcfchgvbhvgkhbh";
    echo $username.'<br>';
    try{
      $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
      $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
      $sql = "SELECT * FROM users WHERE username = :username And password = :password";

      $stmt = $con->prepare( $sql );
      $stmt->bindValue( "username", $username, PDO::PARAM_STR );
      $stmt->bindValue( "password", hash("sha256", $password . $salt), PDO::PARAM_STR );
      $stmt->execute();

      $valid = $stmt->fetch();
      echo '<br> it fetches'.$valid['username'];
      print_r($valid);
      $con = null;
      if( $valid ) {
        echo '<br> its valid';
        print_r($valid);
        $_SESSION['user'][0] = $valid['username'];
        if (isset( $_SESSION['errors'] )){unset($_SESSION['errors']);}
        //if(!empty($_SESSION['LogUrl'])){header("Location: ../{$_SESSION['LogUrl']}");}
        else{header("Location:   ../index.php"); }
      } else {
        $_SESSION['errors'] = 'AuthLogin';
        header("Location: AuthPage.php");
      }
    }
    catch (PDOException $e) {
      echo "chian ".$e->getMessage();
    }
  } else {
    echo 'Oops SeEye went blind!!!';
  }
?>

Here is my registration script just incase there's a change to my password that happens which i'm oblivious too...

  <?php
  include( '../config.php' );
  //Include The Database Connection File

  if( (isset( $_POST['register'] )) && empty($_SESSION['user']))//If a username has been submitted
   {
    $username = $_POST['usernam'];//Some clean up :)
    $password = $_POST['password'];//Some clean up :)
    $salt = "ghvhgcfchgvbhvgkhbh";

  try{
    $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
    $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
    $sql = "SELECT * FROM users WHERE username='.$username.'";

    $stmt = $con->prepare( $sql );

    $stmt->execute();

    $row  = $stmt-> fetch();
    $con = null;
    if( !$row) {
            try {
               $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
               $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
               $sql = "INSERT INTO users(username, password, Date_Joined)
               VALUES(:username, :password,   :Date_Joined)";

   $stmt = $con->prepare( $sql );
   $stmt->bindValue( "username", $username, PDO::PARAM_STR );
   $stmt->bindValue( "password", hash("sha256", $password . $salt), PDO::PARAM_STR );
   $stmt->bindValue( "Date_Joined", date("Y-m-d"), PDO::PARAM_STR );
   $stmt->execute();
   $con = null;
   session_start();
   $_SESSION['user'][0] = $_POST['usernam'];
   if (isset( $_SESSION['errors'] )){unset($_SESSION['errors']);}
     if(!empty($_SESSION['LogUrl'])){header("Location: {$_SESSION['LogUrl']}");}
      else{header("Location: ../index.php"); }
  }catch( PDOException $e ) {
     echo $e->getMessage();
   }
  }
   else
      {
        echo '0ops something went wrong';//No Record Found - Username is available
      }
 }catch (PDOException $e) {
 echo $e->getMessage();
 }
} else {
    echo 'Oops SeEye went blind!!!';
  }
?>

Thank You in advance again