i didn't have a chance to test the previous code. try this:
<?
$file_name = "nieuws.txt";
$fp=fopen("$file_name", "r+"); #open and place the $fp point at the beginning of the file
flock($fp, 2); #prevent the file from being messed up.
$old_data = fread($fp, filesize($file_name)); #read in the old data
rewind($fp); # reset the file pointer to the start of the file so that the fwrite overwrites the original data
fwrite($fp, "new data" . "$old_data"); #concat the new data then the old data
flock($fp,3); #release the lock, fclose can also do this
fclose($fp); #close the file
?>
look at the fopen manual page for a description of the modes.
http://www.php.net/manual/en/function.fopen.php