Fix WordPress "Critical Error"

Understanding the Error

WordPress 5.2+ shows this instead of white screen.

Step 1: Enable Debug Mode

Add to wp-config.php:

define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', true);

Check error log:

sudo tail -f /var/www/wordpress/wp-content/debug.log

Step 2: Check Email for Details

WordPress sends error details to admin email.

Step 3: Recovery Mode

Visit login URL - WordPress may offer "Recovery Mode" link in email or at:

https://yourdomain.com/wp-login.php?action=enter_recovery_mode

Step 4: Disable Problematic Plugin/Theme

# Via WP-CLI
wp plugin deactivate suspect-plugin

# Or rename plugins folder
mv wp-content/plugins wp-content/plugins_backup

Step 5: Increase Memory Limit

define('WP_MEMORY_LIMIT', '256M');

Step 6: Check PHP Version Compatibility

php -v
# Upgrade PHP if needed
sudo add-apt-repository ppa:ondrej/php
sudo apt update
sudo apt install php8.2

Step 7: Reinstall WordPress Core

wp core download --force