m4f1

$text_lenght = 3;
$charset = 'abc';
$charset_length = strlen($charset);

function recurse($width, $position, $base_string)
{
    global $text_lenght, $charset, $charset_length;
     
    for ($i = 0; $i < $charset_length; ++$i) {
        if ($position  < $width - 1) {
            recurse($width, $position + 1, $base_string . $charset[$i]);
        }
    if (strlen($base_string . $charset[$i]) <= $text_lenght) {
      echo $base_string . $charset[$i].'</br>';
    }		

    }
}

recurse($text_lenght, 0, '');