Title: Incorrect cache engine with WEBP Image conversion
Last modified: August 21, 2023

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# Incorrect cache engine with WEBP Image conversion

 *  Resolved [Mikko Raassina](https://wordpress.org/support/users/mraassin/)
 * (@mraassin)
 * [2 years, 9 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/)
 * The W3 Total Cache Image conversion service stopped working a few weeks ago on
   my WordPress/WooCommerce app. It worked out well earlier. I am using PHP 8.2 
   and Memcached, and W3 Total Cache version 2.4.1.
 * In the media library, it says it is still processing images. It has been stuck
   for weeks.
 * I can see quite a few error messages in the Apache log file:
 * Got error ‘PHP message: PHP Warning: Incorrect cache engine in /path/to/my/webapp/
   wp-content/plugins/w3-total-cache/Cache.php on line 74’, referer: [https://…/wp-admin/upload.php](https://…/wp-admin/upload.php)
 * Has anyone come across this error message?
 * Is there a way to get this fixed without losing any WEBP images that have already
   been converted from PNG to WEBP format? I’ve hundreds, if not thousands, images
   that have already been converted and attached to products. I would not like to
   have to attach the pictures one by one again.

Viewing 4 replies - 1 through 4 (of 4 total)

 *  Thread Starter [Mikko Raassina](https://wordpress.org/support/users/mraassin/)
 * (@mraassin)
 * [2 years, 9 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/#post-16988147)
 * EDIT:
   I went through the options, and under Performance / General Settings, I
   scrolled down to the Fragment Cache and changed the Fragment Cache Method from
   none to Memcached.
 * After changing this setting, all error messages disappeared, and the image conversion
   worked out again.
 *  Plugin Contributor [Marko Vasiljevic](https://wordpress.org/support/users/vmarko/)
 * (@vmarko)
 * [2 years, 9 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/#post-16989281)
 * Hey [@mraassin](https://wordpress.org/support/users/mraassin/)
 * Thank you for reaching out and thank you for providing this information.
   We are
   aware of the php warning that is thrown inf the Fragment Cache caching method
   is not selected.
 * This will be fixed in the next release.
 * Glad to know everything is working fine now.
 * Thanks!
 *  Thread Starter [Mikko Raassina](https://wordpress.org/support/users/mraassin/)
 * (@mraassin)
 * [2 years, 9 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/#post-16991690)
 * Thanks [@vmarko](https://wordpress.org/support/users/vmarko/)
 * No sweat! Everything is working fine right now, and happy to hear this gets fixed
   in the next release.
 * Enjoy your week! 🙂
   Mikko
 *  [jpship](https://wordpress.org/support/users/jpship/)
 * (@jpship)
 * [2 years, 4 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/#post-17387119)
 * [@vmarko](https://wordpress.org/support/users/vmarko/) Fragment Cache is a premium
   feature. Does this mean that Image conversion is now a premium feature too? Because
   this combo box cannot be selected in the free version.

Viewing 4 replies - 1 through 4 (of 4 total)

The topic ‘Incorrect cache engine with WEBP Image conversion’ is closed to new replies.

 * ![](https://ps.w.org/w3-total-cache/assets/icon-256x256.png?rev=1041806)
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 * 4 replies
 * 3 participants
 * Last reply from: [jpship](https://wordpress.org/support/users/jpship/)
 * Last activity: [2 years, 4 months ago](https://wordpress.org/support/topic/incorrect-cache-engine-with-webp-image-conversion/#post-17387119)
 * Status: resolved