Title: unable activate cache Last modified: December 14, 2018 --- # unable activate cache * Resolved [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 6 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/) * Hello all * No cache plugins work with my site under development ( w3 total cache, wp super cache, hummingbird …) * With hummingbird the problem start when enable caching option * When I activate and want to visit a page other than the index I have this error: * > PHP Fatal error: Call to a member function get() on null in /var/www/wp-includes/ > cache.php on line 123, referer: [https://domain.fr/](https://domain.fr/) * It’s this function : * ``` function wp_cache_get( $key, $group = '', $force = false, &$found = null ) { global $wp_object_cache; return $wp_object_cache->get( $key, $group, $force, $found ); } ``` * WordPress 4.9.8 wp-config.php : * ``` define( 'WP_DEBUG', true ); define( 'WP_CACHE', true ); ``` * Related issue : [https://wordpress.org/support/topic/unable-activate-cache/#post-10988797](https://wordpress.org/support/topic/unable-activate-cache/#post-10988797)( I was recommended to write here ) * Any idea ? * Thanks ! Will - This topic was modified 7 years, 6 months ago by [lawix](https://wordpress.org/support/users/lawix/). Viewing 15 replies - 1 through 15 (of 17 total) 1 [2](https://wordpress.org/support/topic/unable-activate-cache-2/page/2/?output_format=md) [→](https://wordpress.org/support/topic/unable-activate-cache-2/page/2/?output_format=md) * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996622) * Hi [@lawix](https://wordpress.org/support/users/lawix/), * You are saying that your site is “under development”? Are you referring to some mode on your host or a plugin, or maybe a localhost install? The error you are getting seems to be related to an object cache plugin that you might be using and it’s not working in the development environment. Could you please check to see if an object-cache.php file exists in the wp-content directory? If it does, try to rename it and check if the error goes away. * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996693) * Hello * Under development means to me no in production I can not give you a URL * During a recursive grep on “object-cache”, I don’t have results except the following wordpress functions * ``` ../wp-admin/includes/plugin.php: 'object-cache.php' => array( __( 'External object cache.' ), true ), // auto on load ../wp-includes/load.php: * If an object-cache.php file exists in the wp-content directory, ``` * Thanks * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996776) * [@lawix](https://wordpress.org/support/users/lawix/), * As I said in my previous post, the error is related to object caching, which Hummingbird does not use. If you are sure that there is no plugin that is utilizing the object-cache.php file, I would suggest contacting your host support and ask if there is any server side object caching software installed (Memcached, Redis, etc..). Could be a misconfiguration error. * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996863) * I’m server adminsitrator and not have memcache installed on this machine :/ * William * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996884) * [@lawix](https://wordpress.org/support/users/lawix/), * Unfortunately, just from the error I can only tell that it is caused by an object cache conflict in WordPress (not Hummingbird). You can try and do a plugin/theme conflict tests, by disabling all plugins and enabling them one by one to try figure out which one is causing the issue. But it could be a server misconfiguration as well, because, as you were saying, all other caching plugins lead to similar errors. Can you provide a list of all installed packages on your server? Might be a large list, so it’s better to paste it to a file and link it here. * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996934) * I have disabled all plugin and it’s same probleme * Do you still want the list? (ten are mine) * William - This reply was modified 7 years, 5 months ago by [lawix](https://wordpress.org/support/users/lawix/). * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996942) * [@lawix](https://wordpress.org/support/users/lawix/), * If disabling the plugins doesn’t resolve this, it’s probably a server issue. Yes, please post the list, I’ll take a look. * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996951) * I have this error, I do not know if I had it before : * > PHP Notice: Trying to get property of non-object in /…/wp-content/plugins/hummingbird- > performance/core/modules/class-module-page-cache.php on line 598, referer: … * It’s this function : * ``` private static function skip_page_type() { global $wphb_cache_config; 598: if ( ! is_array( $wphb_cache_config->page_types ) ) { return false; } ``` * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996960) * Plugin list : * ``` +------------------------------+----------+--------+---------+ | name | status | update | version | +------------------------------+----------+--------+---------+ | advanced-custom-fields | inactive | none | 5.7.8 | | advanced-gutenberg | inactive | none | 1.8.2 | | advanced-sidebar-menu | inactive | none | 7.4.3 | | ajax-search-lite | inactive | none | 4.7.20 | | authldap | inactive | none | 2.0.3 | | child-theme-configurator | inactive | none | 2.3.0.4 | | custom-post-type-ui | inactive | none | 1.6.1 | | fg-spip-to-wp | inactive | none | 2.35.0 | | gutenberg | inactive | none | 4.7.0 | | heartbeat-control | inactive | none | 1.2.5 | | hummingbird-performance | active | none | 1.9.3 | | irit-actu | inactive | none | 0.1 | | irit-card | inactive | none | 0.1 | | irit-charts | inactive | none | 0.1 | | irit-equipes | inactive | none | 0.1 | | irit-equipes-gutenberg | inactive | none | 1.0 | | irit-orgchart | inactive | none | 0.1 | | irit-projets | inactive | none | 0.1 | | irit-publis | inactive | none | 0.1 | | irit-config | inactive | none | 1.2 | | leaflet-map | inactive | none | 2.11.5 | | siteorigin-panels | inactive | none | 2.9.7 | | polylang | inactive | none | 2.5 | | post-type-switcher | inactive | none | 3.1.0 | | recent-posts-widget-extended | inactive | none | 0.9.9.7 | | so-widgets-bundle | inactive | none | 1.13.4 | | tabs-widget-for-page-builder | inactive | none | 1.2.1 | | tinymce-advanced | inactive | none | 4.8.2 | | wps-hide-login | inactive | none | 1.5.1 | | wp-statistics | inactive | none | 12.5.6 | | wordpress-seo | inactive | none | 9.2.1 | | advanced-cache.php | dropin | none | | +------------------------------+----------+--------+---------+ ``` - This reply was modified 7 years, 5 months ago by [lawix](https://wordpress.org/support/users/lawix/). * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10996972) * [@lawix](https://wordpress.org/support/users/lawix/), * The error in HB is from the setting global not being initialized properly. But at that point it should already be initialized. It could be caused by the previous error that you were posting. So it is better to resolve the first error and check if it might be the cause of other issues. * Please post the list of server packages, not plugins. I need to verify that you do not have conflicts with any server caching software. * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10997069) * There are more than 20 wordpress on this server, I just checked on another site, with the same plugin, it works and no error in the logs This is not a problem of server and package, but my configuration of this wordpress * William * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10997181) * [@lawix](https://wordpress.org/support/users/lawix/), * Sorry, but I’m just trying to give you some steps that might help in finding the root of the problem. The error message is too generic to pinpoint to a certain plugin or a configuration issue. If it’s not replicated on other sites on the same server, could it be a configuration option you have in wp-config.php file? Have you tried resetting the file to a default state (only copying in the database config)? * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10997256) * Yes and I thank you 🙂 * wp-config.php is stardard, I removed debug config * I’m now checking the integrity of all wordpress files in case * Thanks * [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * (@vanyukov) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10997275) * [@lawix](https://wordpress.org/support/users/lawix/), * You could also try to do a completely new WordPress install, verify that it is working properly, install Hummingbird, verify that all is good, import content, install plugins, etc… * Best regards, Anton * Thread Starter [lawix](https://wordpress.org/support/users/lawix/) * (@lawix) * [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/#post-10998314) * I just found the problem. It appears when the child theme is active. * If I disable it, the page loads and the cache registers. When I re-activate the theme, the cached page works but not the others. * Is there a particular way to design a child theme with a cache system? * William Viewing 15 replies - 1 through 15 (of 17 total) 1 [2](https://wordpress.org/support/topic/unable-activate-cache-2/page/2/?output_format=md) [→](https://wordpress.org/support/topic/unable-activate-cache-2/page/2/?output_format=md) The topic ‘unable activate cache’ is closed to new replies. * ![](https://ps.w.org/hummingbird-performance/assets/icon-256x256.gif?rev=2633221) * [Hummingbird Performance - Cache & Page Speed Optimization for Core Web Vitals | Critical CSS | Minify CSS | Defer CSS Javascript | CDN](https://wordpress.org/plugins/hummingbird-performance/) * [Frequently Asked Questions](https://wordpress.org/plugins/hummingbird-performance/#faq) * [Support Threads](https://wordpress.org/support/plugin/hummingbird-performance/) * [Active Topics](https://wordpress.org/support/plugin/hummingbird-performance/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/hummingbird-performance/unresolved/) * [Reviews](https://wordpress.org/support/plugin/hummingbird-performance/reviews/) * 17 replies * 2 participants * Last reply from: [Anton Vanyukov](https://wordpress.org/support/users/vanyukov/) * Last activity: [7 years, 5 months ago](https://wordpress.org/support/topic/unable-activate-cache-2/page/2/#post-10998524) * Status: resolved