Help with php in wordpress

I’m hoping someone can help me with this as I am sure it is easy and I just don’t know what I am doing. I am using the simplepress plug-in for wordpress and am trying to ad adsense ads to any forums posts. I read the instructions on their site but am having problems still. When I save the php file and upload it to the hooks folder within the plug-ins folder it doesn’t work. Instead of placing the ad in the post it places it in the header for every page of the site. Below is what displays in the header.

{function sf_hook_first_post($forumid, $topicid) $x = ’ '; return $x; }
Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/content/61/6669961/html/wp-content/plugins/simple-forum/forum/hooks/sf-hook-template.php:5) in /home/content/61/6669961/html/wp-content/plugins/wp-responder-email-autoresponder-and-newsletter-plugin/wpresponder.php on line 269

And this is the code in the file I am uploading.

{function sf_hook_first_post($forumid, $topicid)

$x = ‘<script type=“text/javascript”><!–
google_ad_client = “pub-XXXXXXXXXXXX”;
/* 234x60, created 9/8/10 */
google_ad_slot = “1443406738”;
google_ad_width = 234;
google_ad_height = 60;
<script type=“text/javascript”

return $x;