Généré login et mot de passe automatiquement dans BD

Bonjour,

svp comment généré login et mot de passe automatiquement dans BD et voila mon cod:
<?php

if( isset($_POST['submit'])){
$nom = htmlentities(trim($_POST['nom']));
$prenom =htmlentities(trim($_POST['prenom']));
$username = uniqid() ;
$password = md5(uniqid());
$email =htmlentities(trim($_POST['email']));
$societe =htmlentities(trim($_POST['societe']));
$fnc =htmlentities(trim($_POST['fnc']));
$num =htmlentities(trim($_POST['num']));

if ($nom&&$prenom&&$username&&$email&&$societe&&$fnc&&$num)
{
include_once ("connexion.php");
$resultat =
mysql_query('insert into contact(nom,prenom,email,societe,fnc,num) values ("'.$nom.'", "'.$prenom.'","'.$username.'" ,"'.$password.'" "'.$email.'", "'.$societe.'", "'.$fnc.'","'.$num.'")');
die( "inscription terminer" );

}
}



?>
rep svp c urgent