function myCmp($a, $b) {
$nameCmp = strnatcasecmp($a['Name'], $b['Name']);
$ageCmp = strnatcasecmp($a['Age'], $b['Age']);
$codeCmp = strnatcasecmp($a['Code'], $b['Code']);
if ($nameCmp != 0) // Names are not equal
return($nameCmp);
// Names are equal, let's compare age
if ($ageCmp != 0) // Age is not equal
return($ageCmp * -1); // Invert it since you want DESC
// Ages are equal, we don't need to compare code, just return the comparison result
return($codeCmp);
}