It doesn't look like you have support for ranges or negative values.

IE:
gettok("hello there what's up",2-3," ") -> there what's
gettok("hello there what's up",-1," ") -> up

Maybe something you could look into. I had made a gettok that supported ranges a while back. i'll try and find it or remake it .

EDIT:

I took the liberty of doing my best to remake what i had and this is what i came up with.

function gettok($string,$n,$c) {
        if(is_numeric($c)) {
            $c = chr($c);
        }
        $tok = explode($c,$string);
        if($n==0) {
            return count($tok);
        }
        if($n < 0) {
            $n = count($tok)-$n;
        }
        if(@preg_match("#(\d+)-(\d+)?#",$n,$range)) {
            $text = "";
            if(count($range[1])==1) {
                $r1 = $range[1][0]-1;
                $r2 = count($tok);
            }   else    {
                $r1 = $range[1][0]-1;
                $r2 = $range[1][1];
            }
            while($r1<$r2) {
                $text .= $tok[$r1];
                $r1++;
            }
            return $text;
        }
        if(empty($tok[$n-1])) {
            return FALSE;
        }   else    {
            return $tok[$n-1];
        }
    }