modify php natcasesort so 'letters only' come first

Question

I have an array

$arr=array(
"Mega XYZ no number",
"Classic no Number",
"Doppel 80x200cm",
"Classic 100x200cm",
"Mega 240x250",
"Classic 85x200cm",
"Mega 40x250",
"Profi 60x235cm",
"Mega 140x250",
);

and would like to have the following order:

Classic no Number   
Classic 85x200cm  
Classic 100x200cm    
Doppel 80x200cm  
Mega XYZ no number  
Mega 40x250  
Mega 140x250  
Mega 240x250    
Profi 60x235cm 

php's function natcasesort() almost gets it done right EXCEPT 'Classic no Number' and 'Mega XYZ no number' won't be the first in their 'group'! I'd like to have items without any number in it to appear before their alphabetically group-items with numbers.

Answer 1

That's it:

function cmp($a, $b) {
    if ($a == $b) {
        return 0;
    }
    $arr1 = str_split($a);
    $arr2 = str_split($b);

    $number1 = "";
    $number2 = "";

    for($i = 0; $i < count($arr1); $i++){
        $char1 = $arr1[$i];
        $char2 = $arr2[$i];
        if(is_numeric($char1) && !is_numeric($char2)){
            return 1;
        }
        if(!is_numeric($char1) && is_numeric($char2)){
            return -1;
        }
        else if(is_numeric($char1) && is_numeric($char2)){
            $number1 .= $char1;
            $number2 .= $char2;
        }
        else {
            if($char1 != $char2){
                if(!empty($number1) && !empty($number2)){
                    $number1 = intval($number1);
                    $number2 = intval($number2);
                    return ($number1 < $number2) ? -1 : 1;
                }
                return ($char1 < $char2) ? -1 : 1;
            }
            else {
                if(!empty($number1) && !empty($number2) && $number1 != $number2){
                    $number1 = intval($number1);
                    $number2 = intval($number2);
                    return ($number1 < $number2) ? -1 : 1;
                }
            }
        }
    }
}

usort($arr, "cmp");