{"id":1789,"date":"2017-09-12T21:59:16","date_gmt":"2017-09-12T16:29:16","guid":{"rendered":"https:\/\/pheonixsolutions.com\/blog\/?p=1789"},"modified":"2026-09-06T16:01:05","modified_gmt":"2026-09-06T10:31:05","slug":"fatal-error-call-undefined-function-request_filesystem_credentials-wordpress","status":"publish","type":"post","link":"https:\/\/pheonixsolutions.com\/blog\/fatal-error-call-undefined-function-request_filesystem_credentials-wordpress\/","title":{"rendered":"Fatal error: Call to undefined function request_filesystem_credentials() in wordpress"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Introduction<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This guide explains how to <strong>fix &#8220;Fatal error: Call to undefined function request_filesystem_credentials()&#8221;<\/strong> in WordPress \u2014 an error that typically appears during a plugin update, theme installation, or any operation touching WordPress&#8217;s filesystem credential-handling code.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The short version of what&#8217;s happening: <code>request_filesystem_credentials()<\/code> is a function defined inside a specific WordPress core file, <code>wp-admin\/includes\/file.php<\/code>. If that file is missing, incomplete, or corrupted, PHP has no definition for the function, and any code path calling it \u2014 core updates, plugin installers, theme installers \u2014 fails immediately with this fatal error.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Implementation<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">I. Prerequisites<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Before you fix this error, make sure you have:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>FTP, SFTP, or file manager access to your WordPress site&#8217;s files<\/li>\n\n\n\n<li>A backup of your current WordPress files and database before making changes<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">II. How This Fits Into WordPress&#8217;s Architecture<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>WordPress core includes a <strong>filesystem abstraction layer<\/strong>, letting the same code work whether files are written via direct access, FTP, or SSH<\/li>\n\n\n\n<li><code>wp-admin\/includes\/file.php<\/code> defines this layer&#8217;s key functions, including <code>request_filesystem_credentials()<\/code><\/li>\n\n\n\n<li><strong>Plugin installers, theme installers, and the core updater<\/strong> all call into this file when writing files to disk<\/li>\n\n\n\n<li>If the file is missing or broken, every dependent operation fails with the same fatal error, even though the actual problem is isolated to one file<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-scaled.png\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"512\" src=\"https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-1024x512.png\" alt=\"\" class=\"wp-image-11421\" srcset=\"https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-1024x512.png 1024w, https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-300x150.png 300w, https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-768x384.png 768w, https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-1536x768.png 1536w, https:\/\/pheonixsolutions.com\/blog\/wp-content\/uploads\/2017\/09\/wordpress_filesystem_credentials_architecture-1-2048x1024.png 2048w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/a><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">III. Important: Match Your Exact WordPress Version First<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This is the detail the original quick-fix advice gets wrong: <strong>downloading the latest WordPress version and pulling <code>file.php<\/code> from it is not correct if your site isn&#8217;t already on the latest version.<\/strong> Core files are versioned as a matched set \u2014 mixing a newer file into an older installation can introduce new incompatibilities rather than fixing the problem cleanly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Confirm your site&#8217;s exact current version first:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Via WP-CLI:<\/strong><\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">wp core version\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Via direct file inspection<\/strong> (if the dashboard won&#8217;t load):<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">grep \"wp_version =\" wp-includes\/version.php\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Download the <strong>exact version this returns<\/strong> from the <a href=\"https:\/\/wordpress.org\/download\/releases\/\" target=\"_blank\" rel=\"noopener\">official WordPress release archive<\/a> \u2014 not simply &#8220;the latest&#8221; release.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">IV. Verify Core File Integrity (Recommended)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Rather than assuming only <code>file.php<\/code> is affected, check whether other core files were also impacted:<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">wp core verify-checksums\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">This lists any files that don&#8217;t match the official release for your version, giving you a complete picture instead of guessing from a single error message.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">V. Replace file.php<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">From the matching WordPress version, locate:<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">wp-admin\/includes\/file.php\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Upload it via FTP\/SFTP to the same path on your live site, overwriting the existing file completely.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">VI. Fix File Permissions<\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">chmod 644 wp-admin\/includes\/file.php\nchown www-data:www-data wp-admin\/includes\/file.php\n<\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Adjust the ownership user\/group to match whatever user your web server process actually runs as (varies by host \u2014 common alternatives include <code>apache<\/code> or a cPanel-assigned username).<\/p>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\">VII. Clear OPcache<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">If PHP&#8217;s OPcache cached the broken file&#8217;s absence, replacing it on disk alone may not be enough:<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">sudo systemctl restart php-fpm\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Also clear any WordPress caching plugin&#8217;s cache through its dashboard settings.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">VIII. Verify the Fix<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Reload your site and specifically retest an operation that previously triggered the error \u2014 installing or updating a plugin is a common trigger.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">IX. Troubleshooting<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Still failing after replacing file.php:<\/strong> Re-run <code>wp core verify-checksums<\/code> \u2014 other core files may also need replacing, following the same version-matching principle.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Other unexpected files or changes present:<\/strong> Treat this as a potential security incident rather than routine corruption. Run a malware scan and review recent admin activity before assuming it&#8217;s a simple interrupted update.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Full core replacement:<\/strong> WordPress&#8217;s own <strong>Dashboard \u2192 Updates \u2192 Re-install Now<\/strong> re-downloads all core files matching your current version \u2014 often faster than replacing files one at a time if several are affected.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">X. Conclusion<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This error comes down to one core file \u2014 <code>wp-admin\/includes\/file.php<\/code> \u2014 being missing or corrupted, usually from an interrupted upload or update. The detail that actually matters is replacing it with the file from your site&#8217;s <strong>exact current WordPress version<\/strong>, not simply the latest release, and verifying with a checksum check rather than assuming only one file is affected.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently Asked Questions<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Can I just download the latest WordPress version instead of matching my exact version?<\/strong> Not recommended \u2014 core files are versioned as a matched set, and a newer file in an older installation can create new compatibility issues rather than resolving the original problem.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>What if I don&#8217;t know my exact WordPress version because the dashboard won&#8217;t load?<\/strong> Check <code>wp-includes\/version.php<\/code> directly via FTP \u2014 it contains the exact version string even when the dashboard itself is inaccessible.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Is this error a sign my site has been hacked?<\/strong> Not necessarily \u2014 an interrupted update is the more common cause. But if you can&#8217;t explain the missing file through any update or transfer you performed, run a security check to rule out compromise.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Will reinstalling WordPress core delete my content or settings?<\/strong> No \u2014 core file replacement only touches WordPress&#8217;s own core files, not your themes, plugins, media, or database content.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Talk to Our Technology Experts<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Dealing with a stubborn WordPress error or looking for more reliable site management overall? Our team can help with WordPress troubleshooting, site security, performance optimization, and ongoing maintenance support.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/pheonixsolutions.com\/contact\">Connect with our technology experts.<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Related Articles<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/pheonixsolutions.com\/blog\/install-squirrelmail-centos\/\">Install SquirrelMail on CentOS<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/pheonixsolutions.com\/blog\/phpmyadmin-configuration-storage-not-completely-configured-extended-features-deactivated\/\">Fix phpMyAdmin Configuration Storage Error<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/pheonixsolutions.com\/blog\/block-wordpress-login-attacks-csf\/\">Block WordPress Login Attacks on CSF<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Introduction This guide explains how to fix &#8220;Fatal error: Call to undefined function request_filesystem_credentials()&#8221; in WordPress \u2014 an error that [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1022],"tags":[167],"class_list":["post-1789","post","type-post","status-publish","format-standard","hentry","category-web-architecture","tag-wordpress-2","psol-cat-web-architecture"],"jetpack_publicize_connections":[],"jetpack_shortlink":"https:\/\/wp.me\/phn2x7-sR","jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts\/1789","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/comments?post=1789"}],"version-history":[{"count":2,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts\/1789\/revisions"}],"predecessor-version":[{"id":11422,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/posts\/1789\/revisions\/11422"}],"wp:attachment":[{"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/media?parent=1789"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/categories?post=1789"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pheonixsolutions.com\/blog\/wp-json\/wp\/v2\/tags?post=1789"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}