Error when press in a photo

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Hi. I have a problem. When i press in the thumbnail of a product i get this error:

 

Fatal error: Cannot redeclare do_magic_quotes_gpc() (previously declared in /home/shop/public_html/includes/functions/compatibility.php:23) in /home/shop/public_html/includes/functions/compatibility.php on line 23

 

I have look in all files but i can't find the problem.

 

Any idea ?

 

Thanks!