Session no me funciona

[Dalam]

usa una consulta a la base de datos para que te devuelva el numero de resultados que se obtiene

$sql = "SELECT * FROM usuario WHERE nick = '".$usuario ."' AND pass = '".$pass ."' AND id_rol = '".$rol."'";
$sql_query = 'SELECT COUNT(*) AS NUMBER_OF_ROWS FROM (' . $sql . ')';
$stmt= oci_parse($conexion, $sql_query);
oci_define_by_name($stmt, 'NUMBER_OF_ROWS', $number_of_rows);
oci_execute($stmt);
oci_fetch($stmt);
if($number_of_rows < 1) header("Location:index_login.php");