{"id":19021334,"date":"2026-09-16T08:28:22","date_gmt":"2026-09-16T08:28:22","guid":{"rendered":"https:\/\/wordpress.org\/support\/?post_type=topic&#038;p=19021334"},"modified":"2026-09-16T09:29:30","modified_gmt":"2026-09-16T09:29:30","slug":"multisite-755","status":"publish","type":"topic","link":"https:\/\/wordpress.org\/support\/topic\/multisite-755\/","title":{"rendered":"Multisite"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Hi everyone,<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">I opened this ticket some time ago: <a href=\"https:\/\/wordpress.org\/support\/topic\/plugins-problem-in-multisite-installation\/\">https:\/\/wordpress.org\/support\/topic\/plugins-problem-in-multisite-installation\/<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The problem was never resolved, and I am still running version 6.14.2 because I cannot upgrade to any newer version.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">I keep getting the following error:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&#091;16-Sep-2026 07:23:00 UTC] PHP Fatal error:  Cannot redeclare check_upload_size() (previously declared in \/home\/www\/multisite\/htdocs\/wp-admin\/includes\/ms.php:18) in \/home\/www\/multisite\/htdocs\/wp-admin\/includes\/ms.php on line 18\n&#091;16-Sep-2026 07:23:26 UTC] PHP Fatal error:  Cannot redeclare check_upload_size() (previously declared in \/home\/www\/multisite\/htdocs\/wp-admin\/includes\/ms.php:18) in \/home\/www\/multisite\/htdocs\/wp-admin\/includes\/ms.php on line 18<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">With other plugins, I have been able to work around similar issues by commenting out a line such as this one:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ Load WP user management functions\nif ( is_multisite() ) {\n    \/\/ require_once( ABSPATH . 'wp-admin\/includes\/ms.php' );  &lt;---- this one!\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">However, in this case I cannot find any reference to anything similar.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">I am particularly concerned because of the latest security vulnerability reported by Wordfence, as I am unable to update to a newer version.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Does anyone have any idea what could be causing this <code>Cannot redeclare check_upload_size()<\/code> error or how I could fix it so that I can update?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The error occurs when logging in. If I do not log in, there are no errors and the website looks fine. However, as soon as I enter a username and password and log in, the <strong>FATAL ERROR<\/strong> appears.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Thanks in advance for any help.<\/p>\n","protected":false},"template":"","class_list":["post-19021334","topic","type-topic","status-publish","hentry","topic-tag-multisite"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic\/19021334","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":1,"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic\/19021334\/revisions"}],"predecessor-version":[{"id":19021358,"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/topic\/19021334\/revisions\/19021358"}],"wp:attachment":[{"href":"https:\/\/wordpress.org\/support\/wp-json\/wp\/v2\/media?parent=19021334"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}