{"id":19012124,"date":"2026-09-05T02:09:47","date_gmt":"2026-09-05T02:09:47","guid":{"rendered":"https:\/\/wordpress.org\/support\/topic\/fatal-error-uncaught-error-call-to-undefined-function-wp_is_serving_rest_reque\/"},"modified":"2026-09-05T02:09:47","modified_gmt":"2026-09-05T02:09:47","slug":"fatal-error-uncaught-error-call-to-undefined-function-wp_is_serving_rest_reque","status":"publish","type":"topic","link":"https:\/\/wordpress.org\/support\/topic\/fatal-error-uncaught-error-call-to-undefined-function-wp_is_serving_rest_reque\/","title":{"rendered":"Fatal error: Uncaught Error: Call to undefined function wp_is_serving_rest_reque"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Hello!<br \/>After updating to 5.3.4:<br \/><br \/><strong>Fatal error<\/strong>: Uncaught Error: Call to undefined function wp_is_serving_rest_request() in \/var\/www\/&#8230;.\/wp-content\/plugins\/wp-cloudflare-page-cache\/vendor\/woocommerce\/action-scheduler\/classes\/ActionScheduler_RecurringActionScheduler.php:29 Stack trace: #0 \/var\/www\/&#8230;..\/wp-includes\/class-wp-hook.php(306): ActionScheduler_RecurringActionScheduler-&gt;init() #1 \/var\/www\/&#8230;.\/wp-includes\/class-wp-hook.php(332): WP_Hook-&gt;apply_filters(NULL, Array) #2 \/var\/www\/&#8230;..\/wp-includes\/plugin.php(517): WP_Hook-&gt;do_action(Array) #3 \/var\/www\/&#8230;..\/wp-settings.php(623): do_action(&#8216;init&#8217;) #4 \/var\/www\/&#8230;..\/wp-config.php(95): require_once(&#8216;\/var\/www\/&#8230;..&#8217;) #5 \/var\/www\/&#8230;..\/wp-load.php(50): require_once(&#8216;\/var\/www\/&#8230;&#8230;&#8217;) #6 \/var\/www\/&#8230;..\/wp-admin\/admin.php(34): require_once(&#8216;\/var\/www\/&#8230;&#8230;&#8217;) #7 \/var\/www\/&#8230;&#8230;\/wp-admin\/index.php(10): require_once(&#8216;\/var\/www\/&#8230;&#8230;&#8217;) #8 {main} in <strong>\/var\/www\/&#8230;&#8230;\/wp-content\/plugins\/wp-cloudflare-page-cache\/vendor\/woocommerce\/action-scheduler\/classes\/ActionScheduler_RecurringActionScheduler.php<\/strong> on line <strong>29<\/strong><br \/><br \/><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The Call to undefined function wp_is_serving_rest_request() error occurs because a plugin is trying to use a native WordPress function that does not exist in my current WordPress version. (6.2.11)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So, I think it would be better to limit updates on websites below version 6.5.0 or remove this function from 5.3.4\u2026<\/p>\n","protected":false},"template":"","class_list":["post-19012124","topic","type-topic","status-publish","hentry"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic\/19012124","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic"}],"about":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic\/19012124\/revisions"}],"wp:attachment":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/media?parent=19012124"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}