PHP Warning: mysql_fetch_array() expects parameter 1 to be ....

<?php

if (isset($_POST['register'])) {
  if (isset($_POST['pseudo']) AND !empty($_POST['pseudo']) AND isset($_POST['email']) AND !empty($_POST['email']) AND isset($_POST['pass1']) AND !empty($_POST['pass1']) AND isset($_POST['pass2']) AND !empty($_POST['pass2']) AND isset($_POST['nom']) AND !empty($_POST['nom']) AND isset($_POST['prenom']) AND !empty($_POST['prenom']) AND isset($_POST['birth']) AND !empty($_POST['birth'])) {
    $pseudo = mysql_real_escape_string($_POST['pseudo']);
    $email = mysql_real_escape_string($_POST['email']);
    $pass1 = sha1($_POST['pass1']);
    $pass2 = sha1($_POST['pass2']);
    $nom = mysql_real_escape_string($_POST['nom']);
    $prenom = mysql_real_escape_string($_POST['prenom']);
    $birth = mysql_real_escape_string($_POST['birth']);
    
    if ($pass1 == $pass2) {
      $req1 = mysql_query('SELECT pseudo FROM membres WHERE pseudo = "'.$pseudo.'"');
      $rep1 = mysql_fetch_array($req1);
      if (!isset($rep1['pseudo'])) {
        $req2 = mysql_query('SELECT email FROM membres WHERE email = "'.$email.'"');
        $rep2 = mysql_fetch_array($req2);
        if (!isset($rep2['email'])) {
          $req3 = mysql_query('SELECT nom FROM membres WHERE nom = "'.$nom.'"');
          $rep3 = mysql_fetch_array($req3);
          if (!isset($rep3['nom'])) {
            $register = mysql_query('INSERT INTO membres VALUES("","'.$pseudo.'","'.$email.'","'.$pass1.'","'.$nom.'","'.$prenom.'","'.$birth.'","0","")');
            ?>

            <div class="container">
              <div class="row">
                <div class="alert alert-dismissible alert-success">
                  <button type="button" class="close" data-dismiss="alert">×</button>
                  <h4>Félicitation!</h4>
                  <p>Votre compté est maintenant crée !</p>
                  <br/>
                  <a href="connect.php" class="btn btn-info">Connection</a>
                </div>
              </div>
            </div>

            <?php
          } else {
            $error_nom = 1;
            $error = 'Ce nom est déjà enregistré';
          }
        } else {
          $error_email = 1;
          $error = 'Cet email est déjà enregistré';
        }
      } else {
        $error_pseudo = 1;
        $error = 'Le pseudo est déjà enregistré.';
      }

    } else {
      $error_pass = 1;
      $error = 'Les mots de passe sont différents';
    }

  } else {
    $error_all = 1;
    $error = 'Veuillez remplir tout les champs.';
  }
}