[PHP] Empty delimiter error - ??

[Rich Pinder]

I'm totally unfamiliar with php, and making some slight modificiations
to Chris Heilmann's nice v 1.1 Newsleterscript.

What exactly is meant by an empty delimiter?  This code works just fine,
but I get the following error:

Warning: Empty delimiter in /home/sites/site56/web/trailcrew.php on line
63



# Put the entries into the array lines
$lines = explode("%",$content);
for ($key=1;$key<sizeof($lines);$key++){
# when the email is not in the list, add the old entries
 if (!stristr($lines[$key], $email)) {                    <----
offending line - line 63
  $out .= "%".$lines[$key];
 }
# when it's already in the list, set found
 else {
  $found=1;
 }
}


Thanks
Rich Pinder