php去掉文件前几行的方法

<?php
foreach (new directoryiterator('./') as $fileinfo) {
  if($fileinfo->isdot()) continue;
  if($fileinfo->getextension()=="lrc"){
    $handle = fopen($fileinfo->getfilename(), 'rw');
    $line_num=0;
    while(!feof($handle)){
      $str=fgets($handle, 1024);
      if(strstr($str, "www.99lrc.net")){
        ob_start();
        fpassthru($handle);
        //fclose($handle);
        file_put_contents($fileinfo->getfilename(),ob_get_clean());
        printf('done');
        break;
      }
      $line_num++;
    }
    fclose($handle);
    echo $fileinfo->getfilename() . php_eol;
  }
}