Title: PHP error when cliking on ‘Clean Cache’
Last modified: June 4, 2022
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# PHP error when cliking on ‘Clean Cache’
* Resolved [bernard92000](https://wordpress.org/support/users/bernard92000/)
* (@bernard92000)
* [4 years ago](https://wordpress.org/support/topic/php-error-when-cliking-on-clean-cache/)
* Hello,
* I have an error message into my php_error.log each time I click on ‘Clean Cache’:
* PHP Warning: Undefined array key “host” in /wp-content/plugins/wp-speed-of-light/
src/Cache.php on line 377
PHP Stack trace: PHP 1. {main}() /wp-admin/admin-ajax.
php:0 PHP 2. do_action($hook_name = ‘wp_ajax_wpsol_ajax_preload_cache’) /wp-admin/
admin-ajax.php:187 PHP 3. WP_Hook->do_action($args = [0 => ”]) /wp-includes/plugin.
php:476 PHP 4. WP_Hook->apply_filters($value = ”, $args = [0 => ”]) /wp-includes/
class-wp-hook.php:331 PHP 5. Joomunited/WPSOL/Configuration::startPreloadCache(”)/
wp-includes/class-wp-hook.php:307 PHP 6. Joomunited/WPSOL/Cache::cacheHomePage()/
wp-content/plugins/wp-speed-of-light/src/Configuration.php:242 PHP 7. Joomunited/
WPSOL/Cache::scanLinks($content = ‘