function getPng2PrgOutputFormat(array $output) : string
{
    $convLine = '';
    /*
     * find the line with the converted info
     * png2prg echoes a line like this:
     *
     * converted "INFILE" to "OUFILE" in "FORMAT" format
     *
     * step 1.)     look for a line starting with 'converted'
     */
    foreach ($output as $line)
    {
        if (substr($line, 0, 9) === 'converted')
        {
            $convLine = $line;
            break;
        }
    }

    /*
     * step 2.)     split the line on char " to array
     *              and return element '5' with the FORMAT
     */
    $convLineArr = explode('"', $convLine);
    if (!array_key_exists('5', $convLineArr)) return '';

    return trim($convLineArr['5']);
}

bitmap = $2000
screenram = $3f40
colorram = $4328
d020color = 0
d021color = 1

write 8356 bytes to "q.prg" in "koala" format.