Title: recurring PHP warning
Last modified: October 22, 2025

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# recurring PHP warning

 *  [dkray](https://wordpress.org/support/users/dkray/)
 * (@dkray)
 * [7 months, 1 week ago](https://wordpress.org/support/topic/recurring-php-warning/)
 * I’m experiencing a recurring PHP warning on my WordPress site related to the 
   Cache Enabler plugin. The issue appears even after clearing the cache and reoccurs
   once the cache is rebuilt.
   Warning: preg_match(): Unknown modifier ‘p’ in /home/
   httpd/vhosts/sergesellsretro.ch/shop.sergesellsretro.ch/wp-content/plugins/cache-
   enabler/inc/cache_enabler_engine.class.php on line 352Warning: Cannot modify 
   header information – headers already sent by (output started at /home/httpd/vhosts/
   sergesellsretro.ch/shop.sergesellsretro.ch/wp-content/plugins/cache-enabler/inc/
   cache_enabler_engine.class.php:352) in /home/httpd/vhosts/sergesellsretro.ch/
   shop.sergesellsretro.ch/wp-content/plugins/wpvivid-imgoptim/includes/cdn/class-
   wpvivid-cdn.php on line 50Warning: Cannot modify header information – headers
   already sent by (output started at /home/httpd/vhosts/sergesellsretro.ch/shop.
   sergesellsretro.ch/wp-content/plugins/cache-enabler/inc/cache_enabler_engine.
   class.php:352) in /home/httpd/vhosts/sergesellsretro.ch/shop.sergesellsretro.
   ch/wp-content/plugins/wpvivid-imgoptim/includes/cdn/class-wpvivid-cdn.php on 
   line 55Warning: Cannot modify header information – headers already sent by (output
   started at /home/httpd/vhosts/sergesellsretro.ch/shop.sergesellsretro.ch/wp-content/
   plugins/cache-enabler/inc/cache_enabler_engine.class.php:352) in /home/httpd/
   vhosts/sergesellsretro.ch/shop.sergesellsretro.ch/wp-content/plugins/wpvivid-
   imgoptim/includes/cdn/class-wpvivid-cdn.php on line 56The issue seems to originate
   from the following line inside Cache Enabler:preg_match(‘/^https?://’ . $_SERVER[‘
   HTTP_HOST’] . ‘/’, $url);Thank you very much for your help!

The topic ‘recurring PHP warning’ is closed to new replies.

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 * 0 replies
 * 1 participant
 * Last reply from: [dkray](https://wordpress.org/support/users/dkray/)
 * Last activity: [7 months, 1 week ago](https://wordpress.org/support/topic/recurring-php-warning/)
 * Status: not resolved