Title: PHP Fatal error: Uncaught Error: Call to undefined function __() Last modified: March 23, 2021 --- # PHP Fatal error: Uncaught Error: Call to undefined function __() * Resolved [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/) * I’m getting this error several times a day on my apache logs * [Mon Mar 22 09:52:12.066348 2021] [proxy_fcgi:error] [pid 19860:tid 139858714400512][ client 172.105.161.142:39814] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [https://35.217.65.174/](https://35.217.65.174/) [ Mon Mar 22 11:15:46.914484 2021] [proxy_fcgi:error] [pid 20240:tid 139858714400512][ client 45.146.165.157:53538] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/api/jsonws/invoke](http://35.217.65.174:80/api/jsonws/invoke)[ Mon Mar 22 11:15:52.297810 2021] [proxy_fcgi:error] [pid 19860:tid 139858563331840][ client 45.146.165.157:47158] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/_ignition/execute-solution](http://35.217.65.174:80/_ignition/execute-solution)[ Mon Mar 22 11:15:52.925170 2021] [proxy_fcgi:error] [pid 28669:tid 139858941003520][ client 45.146.165.157:47506] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/console/](http://35.217.65.174:80/console/)[ Mon Mar 22 11:15:53.721200 2021] [proxy_fcgi:error] [pid 28669:tid 139859114813184][ client 45.146.165.157:36806] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/wp-content/plugins/wp-file-manager/readme.txt](http://35.217.65.174:80/wp-content/plugins/wp-file-manager/readme.txt)[ Mon Mar 22 12:28:08.495760 2021] [proxy_fcgi:error] [pid 20240:tid 139858630473472][ client 209.17.96.210:35573] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/](http://35.217.65.174:80/)[ Mon Mar 22 12:43:41.700129 2021] [proxy_fcgi:error] [pid 6927:tid 139858529761024][ client 35.209.212.73:36916] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/_ignition/execute-solution](http://35.217.65.174:80/_ignition/execute-solution)[ Mon Mar 22 12:43:45.204883 2021] [proxy_fcgi:error] [pid 20240:tid 139858605295360][ client 35.209.212.73:37312] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/login](http://35.217.65.174:80/login)[ Mon Mar 22 12:43:46.304540 2021] [proxy_fcgi:error] [pid 20240:tid 139858588509952][ client 35.209.212.73:37312] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/jenkins/login](http://35.217.65.174:80/jenkins/login)[ Mon Mar 22 12:43:48.287451 2021] [proxy_fcgi:error] [pid 19862:tid 139858588509952][ client 35.209.212.73:37662] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174:80/manager/html](http://35.217.65.174:80/manager/html)[ Mon Mar 22 13:09:00.145822 2021] [proxy_fcgi:error] [pid 6927:tid 139858831898368][ client 182.48.105.210:1391] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [https://35.217.65.174.xip.io:443/](https://35.217.65.174.xip.io:443/)[ Mon Mar 22 14:06:12.871006 2021] [proxy_fcgi:error] [pid 6927:tid 139858521368320][ client 193.118.53.194:36382] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [http://35.217.65.174/](http://35.217.65.174/)[ Mon Mar 22 14:38:24.039603 2021] [proxy_fcgi:error] [pid 7501:tid 139858815112960][ client 192.35.168.80:52458] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: Call to undefined function __() in /opt/bitnami/apps/wordpress/ htdocs/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php: 28\nStack trace:\n#0 [internal function]: wpo_cache(”, 9)\n#1 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/wp-optimize/cache/file- based-page-cache-functions.php on line 28’, referer: [https://35.217.65.174:443/](https://35.217.65.174:443/) * I’ve only found [one other thread](https://wordpress.org/support/topic/error-call-to-undefined-function-__-on-attempt-from-alias-domain/) on this but it didn’t have much info or a solution. * I’m not exactly clear what this function is or does. The referrers in these calls also don’t make sense to me. That’s the server IP, but a lot of weird directories I don’t recognize. * I’m runnning a WP multisite distribution by Bitnami on GCP. I have a primary site and the two child sites that are subdomains of the main one. Viewing 8 replies - 1 through 8 (of 8 total) * [Harshad](https://wordpress.org/support/users/bornforphp/) * (@bornforphp) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14226453) * [@gonazar](https://wordpress.org/support/users/gonazar/) Do you have any other cache plugin installed or have caching enabled on server level? If yes can you please disable it temporarily and check if you still see these errors in error logs? * Thread Starter [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14231064) * I used to have pagespeed but I already disabled it, I’m in the process of switching to wp-optimize. * I also had W3 cache installed but not activated. I’ve now deleted it but i’m still getting the errors. * I’ve also completely uninstalled wp-optimize and reinstalled it, and I also tried a settings wipe. * I looked at my wp-config and confirmed I have `define('WP_CACHE', true); // WP- Optimize Cache` at the top of the file. * [Harshad](https://wordpress.org/support/users/bornforphp/) * (@bornforphp) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14231224) * [@gonazar](https://wordpress.org/support/users/gonazar/) Are these appearing recently? Since when you are experiencing this issue? * What were the recent changes you made to your site? * Thread Starter [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14231314) * I get the error about 100-150 times a day and at all times of day/night. It’s been doing it since I installed the plugin a few days ago. * This plugin is the most recent change made. * I have a couple of other support threads open currently on other forums with other issues of my site. [One was focused](https://community.bitnami.com/t/serve-unresponsive-with-very-high-disk-throughput/92796/15) on the errors I was getting from Pagespeed, which ultimately led me to disabling it and trying wp-optimize instead. * [The other thread](https://community.bitnami.com/t/siteurl-resets-to-default-gcp-external-address-when-the-instance-is-stopped-restarted/92819/2) I have going has to something to do with cookies and session data. Our administrators, including myself, have an issue where it logs us out when we use the multisite dropdown to navigate the different sites on the network. I don’t think users are affected though. * I also have a cloudflare thread where I’m trying to figure out geoblocking firewall rules. * Thread Starter [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14236307) * I disabled the plugin for a few hours and I also got this error: * `[Thu Mar 25 13:25:51.163512 2021] [proxy_fcgi:error] [pid 1995:tid 139858672436992][ client 172.70.35.20:46060] AH01071: Got error 'PHP message: PHP Fatal error: Uncaught Error: Class 'getid3_handler' not found in /opt/bitnami/apps/wordpress/ htdocs/wp-includes/ID3/module.audio.ac3.php:18\nStack trace:\n#0 {main}\n thrown in /opt/bitnami/apps/wordpress/htdocs/wp-includes/ID3/module.audio.ac3.php on line 18'` * I don’t think it’s related, but since it’s also a php error I thought I would mention it just in case. * [Harshad](https://wordpress.org/support/users/bornforphp/) * (@bornforphp) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14236900) * [@gonazar](https://wordpress.org/support/users/gonazar/) These errors are getting for WordPress core, Can you please try to change the PHP version and check if you still get the error? * Thread Starter [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14246329) * I’m on version 7.3.13 is that not new enough? * I see wordpress is recommending 7.4 now but I’m concerned about compatibility with my other plugins. * I downloaded and installed the PHP compatibility checker by WP Engine and it doesn’t even have a scan option for 7.4 >__> * Thread Starter [gonazar](https://wordpress.org/support/users/gonazar/) * (@gonazar) * [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14261654) * I don’t think I can update my php, not easily anyways. * I’m running a bitnami stack deployment, which recommends for updating I have to migrate my entire site to a fresh deployment to update the stack dependencies safely. * I’m using a multisite which makes that really difficult so I’m leaning towards not bothering with the update. * Many of the errors in my initial posting were directly related to the wp-optimize plugin. I feel like that other error was just a coincidence. Viewing 8 replies - 1 through 8 (of 8 total) The topic ‘PHP Fatal error: Uncaught Error: Call to undefined function __()’ is closed to new replies. * ![](https://ps.w.org/wp-optimize/assets/icon-256x256.png?rev=1552899) * [WP-Optimize – Cache, Compress images, Minify & Clean database to boost page speed & performance](https://wordpress.org/plugins/wp-optimize/) * [Frequently Asked Questions](https://wordpress.org/plugins/wp-optimize/#faq) * [Support Threads](https://wordpress.org/support/plugin/wp-optimize/) * [Active Topics](https://wordpress.org/support/plugin/wp-optimize/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/wp-optimize/unresolved/) * [Reviews](https://wordpress.org/support/plugin/wp-optimize/reviews/) ## Tags * [php-error](https://wordpress.org/support/topic-tag/php-error/) * 8 replies * 2 participants * Last reply from: [gonazar](https://wordpress.org/support/users/gonazar/) * Last activity: [5 years, 1 month ago](https://wordpress.org/support/topic/php-fatal-error-uncaught-error-call-to-undefined-function-__/#post-14261654) * Status: resolved