<?php
$f = 'pklist.txt';
$fp = fopen($f, 'r+');
$data = fgets($fp);
$contents = fread($fp, filesize($f));
fseek($fp, 0);
fwrite($fp,$contents);
fwrite($fp,$data);
fclose($fp);
?>
That should work..
Open file using r+
Read first line and store to $data
Read the rest and store to $contents (fread will stop once end of file is reach)
Rewind to beginning of file
Write $contents
Write $data
Close file
Note: Also, if you want just a fixed number of characters instead of the entire line. Just change fgets to something like fgets($fp,5) to only move 5 chars.