Código PHP:
<? include "conecta.cfg";
echo $email;
$verifica = mysql_db_query("$sys_dbname","select * from usuarios where email='$email'")or die(mysql_query();
$row_verifica = mysql_fetch_row($verifica);
$correo = $row_verifica[1];
if ($correo >=1){
echo "estado=OK";
session_start();
$_SESSION['email']=$email;
}else{
echo "estado=KO";
}
?>