Espace membre (connexion) Debutant

<?php
session_start();

/* Mysql PDO */

include ("config/config.inc.php");

$req=$connexion->prepare("SLELECT login, pass FROM compte WHERE login =:login && pass =:passwdmd5");

 if (isset($_POST['login']) AND (isset($_POST['pass'])))

  $req->execute(array(
   'login'=>$_POST['login'];
   'passwdmd5'=> (md5($_POST ['pass']))));

   $req2=$req->fetch();
 
  if(!$req2)
 {
  
 
    header("Location: index.php");
  
 }

  else
 {
    header("Location: admin.php") ;
 }
 

 
?>

<?php
session_start();

/* Mysql PDO */

include ("config/config.inc.php");

$req=$connexion->prepare("SLELECT login, pass FROM compte WHERE login =:login && pass =:passwdmd5");

 if (isset($_POST['login']) AND (isset($_POST['pass'])))

  $req->execute(array(
   'login'=>$_POST['login'];
   'passwdmd5'=> (md5($_POST ['pass']))));

   $req2=$req->fetch();

  if(!empty($req2))
 {
    header("Location: admin.php") ;
 }

  else
 {
     header("Location: index.php");
 }
 

<?php
session_start();

/* Mysql PDO */

include ("config/config.inc.php");

$req=$connexion->prepare("SLELECT login, pass FROM compte WHERE login =:login ");
$req->execute(array(
   'login'=>$_POST['login']
    ));
$req=$req->fetch();

if (isset($_POST['login']) AND isset($_POST['pass']))
{
if ($_POST['longin'] == $req['login'] AND (md5($_POST['pass'])) == $req['passwdmd5'])
{
  header("Location: admin.php") ;
}
else
{
  header("Location: index.php");
}