function generate_license($suffix = null) {
    // Default tokens contain no "ambiguous" characters: 1,i,0,o
    if(isset($suffix)){
        // Fewer segments if appending suffix
        $num_segments = 3;
        $segment_chars = 6;
    }else{
        $num_segments = 4;
        $segment_chars = 5;
    }
    $tokens = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';
    $license_string = '';
    // Build Default License String
    for ($i = 0; $i < $num_segments; $i++) {
        $segment = '';
        for ($j = 0; $j < $segment_chars; $j++) {
            $segment .= $tokens[rand(0, strlen($tokens)-1)];
        }
        $license_string .= $segment;
        if ($i < ($num_segments - 1)) {
            $license_string .= '-';
        }
    }
$license = generate_license();
// YF6G2-HJQEZ-8JZKY-8C8ZN

for ($i=0; $i < 4; $i++) {
  for ($q=0; $q < 4; $q++) {
    echo chr(rand(65,90));
  }
  if($i != 3) echo '-';
}