php function ffgets fp while true fgetc fp if return return fp fopen s

<?php                                                                                                                                                                                                        

function ffgets($fp) {
    $r = '';          

    while (true) {
        $c = fgetc($fp);
        $r.= $c;
        if ($c == "\n") return $r;
    }

    return $r;
}

$fp = fopen('source.xml', 'r');

$nextfile_number = 1;

while (!feof($fp)) {

    $line = ffgets($fp);

    $nextfile_number_str  = sprintf('%010d', $nextfile_number);
    $path = "pages/".substr($nextfile_number_str, -1, 1)."/".substr($nextfile_number_str, -2, 1)."/".substr($nextfile_number_str, -3, 1)."/".substr($nextfile_number_str, -4, 1);

    $oldumask = umask(0);

    if (!is_dir($path)) {
       mkdir($path, 0777, true);
    }
    umask($oldumask);

    $nextfile_name = $path."/f".$nextfile_number.".xml";

    if (strstr($line, "<page>")) {

        $nfp = fopen($nextfile_name, 'w');
        fwrite($nfp, $line);

    } elseif (strstr($line, "</page>")){

        fwrite($nfp, $line);
        fclose($nfp);
        $nextfile_number++;
        echo $nextfile_number."\r\n";
    } else {

        fwrite($nfp, $line);

    }

}

fclose($fp);

?>