Script:

<?
$subvar_ar = array("AX_SES_ID" => "049129128921948493289312843");
while(list($key,$val) = each($subvar_ar)) {
  var_dump($key);
}

?>

outputs:

string(9) "AX_SES_ID"

Warning: Cannot use a scalar value as an array in t.php on line 3

Warning: Cannot use a scalar value as an array in t.php on line 3