Activation keys

<?php

$input = explode("&", readline());
$pattern = '/[A-Za-z0-9]{16,24}/';

$keys = [];
$tempStr = "";
for ($i = 0; $i < count($input);$i++){
    if (preg_match($pattern, $input[$i])) {
        for ($j = 0; $j < strlen($input[$i]);$j++){
            if (strlen($input[$i]) === 16) {
                $tempStr .= "-" . substr($input[$i], $j, 4);
                $j = $j + 4 - 1;
            } else if (strlen($input[$i]) === 25) {
                $tempStr .= "-" . substr($input[$i], $j, 5);
                $j = $j + 5 - 1;
            }
        }
        $tempStr = ltrim($tempStr, "-");
        for ($n = 0; $n < strlen($tempStr);$n++) {
            if (ctype_digit($tempStr[$n])) {
                $tempStr[$n] = 9 - $tempStr[$n];
            }
        }
        $tempStr = strtoupper($tempStr);
        $keys[] = $tempStr;
        $tempStr = "";
    }
}
echo implode(", ", $keys);