问PHP/SQL :从数据库收到"false“值，查询良好

EN

<?php
include("../template/pdo.php");
$query = $pdo->prepare("SELECT id_utilisateur FROM utilisateur
      WHERE `mail` IN ( ':mail' )
        AND `mdp` IN ( ':mdp' )");
$query->bindParam(':mail', $_GET['identifiant'], PDO::PARAM_STR);
$query->bindParam(':mdp', $_GET['mdp'], PDO::PARAM_STR);
$success = $query->execute();

if($success)
{
  $result = $query->fetch();
  var_dump($result); //bool(false) actually
  if($result == false){
    $message = "Try again.";
  }
  else{
    $message = "Congratulation !";
  }
}