Call to undefined function (WordPress) 📝 WordPress

WordPress: Fatal error: Uncaught Error: Call to undefined function wp_get_current_user() / add_action() / get_header()

Code called a WordPress function before WordPress loaded, or a theme/plugin file was opened directly.

Seen on: WordPress

Meaning

Plugins must hook into WordPress actions (init, plugins_loaded) rather than calling functions at file load. Loading a PHP file directly (bypassing WordPress) or pluggable functions used too early (wp_get_current_user before plugins_loaded) cause it.

Common causes

  • Function called at plugin load time instead of in a hook
  • PHP file accessed directly by URL
  • Custom script without require wp-load.php
  • Pluggable function used before it’s defined

⚡ Quick fix

  1. Move the call into an appropriate hook (init, wp_loaded)
  2. Never call theme/plugin files directly; use admin-ajax/REST
  3. For standalone scripts, use WP-CLI

Detailed fix by platform

WordPress

  1. php
    add_action('init', function () {
    $user = wp_get_current_user();
});

How to diagnose

  1. Stack — File and line calling it
  2. Entry — Accessed directly?

🔧 Still not fixed?

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