Fatal error: Call to undefined function sha()

<?php

//la function qui va verifier la combinaison pseudo/password

function verifier_combinaison_pseudo_password($pseudo,$password)
{
  $pseudo = htmlspecialchars(strip_tags($_POST['pseudo']));
  $password = htmlspecialchars(strip_tags($_POST['password']));
  $password = sha($password);

  $bdd = new PDO('mysql:host=localhost;dbname=rs;charset=utf8', 'root', '');
    //donc la, la verification:
$req = $bdd->query('SELECT COUNT(*) FROM utilisateurs WHERE pseudo="'.$pseudo.'" AND password="'.$password.'"');
$etat = $req->fetchColumn();  

if($etat == 0){
return 0;
}else{
 return 1;

     }
}

?>