A substitute for str_ireplace() which I wrote to allow its usage on PHP versions below 5.

Usage

$test = str_ireplace("Test", "foo", "test TEST Test t3st");
echo $test; // "foo foo foo t3st"

Code

function str_ireplace($search, $replace, $subject, &$count = null) {
    $search = "#" . addcslashes(preg_quote($search), '#') . "#i";
    if ($count == null) {
        return preg_replace($search, $replace, $subject);
    }
    return preg_replace($search, $replace, $subject, -1, $count);
}