Ok I searched the internet and found an equivalent function to array_change_key_case. Place the code bellow in php4.2 compatibility file or somewhere above the line that produces that error in the includes/Core/security.php file:
if (!function_exists('array_change_key_case')) {
define("CASE_UPPER",1);
define("CASE_LOWER",0);
function array_change_key_case($array,$case=CASE_LOWER) {
if ($case=CASE_LOWER) { $cmd=strtolower; }
elseif ($case=CASE_UPPER) { $cmd=strtoupper; }
foreach($array as $key=>$value) {
$output[$cmd($key)]=$value;
}
return $output;
}
}