[PHP] append line to text file HELP !!!

[Rodrigo]

Ok guys, this is the code and under it you can see what I get when I try
to submit the form. 
 
 
<?php
$file_pointer=file('emails.txt','a') || exit;
$string_to_write = ("$newmail")."\n";
$s=fopen($file_pointer,$string_to_write);
$s=fclose($fp);
?>
 
 
Warning: Supplied argument is not a valid File-Handle resource in
/home/restricted/home/h4ck3r/public_html/write.php on line 4

Warning: Supplied argument is not a valid File-Handle resource in
/home/restricted/home/h4ck3r/public_html/write.php on line 6