Title: PHP Fatal error
Last modified: May 14, 2026

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# PHP Fatal error

 *  Resolved [James](https://wordpress.org/support/users/james-feaver/)
 * (@james-feaver)
 * [1 day, 12 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/)
 * Great plugin which does a lot for performance; however, I am encountering an 
   issue. I fully appreciate at least 4 plugins get a mention here as I am not fully
   clear on where the issue lies. Apologies if it is not yours and for the long 
   and garbled explanation.
 * On the home page of my staging site, I have (for testing) got every plugin enabled
   in Freesoul. When I search using the Relevanssi plugin or with it deactivated
   and using the native WP search (e.g. “cheese”), I get message at top of the page:
 * _WooCommerce plugin must be active for Address Validation & Google Address Auto
   Complete Plugin for WooCommerce(Basic) to work._
 * Debug.log gives the below:
 *     ```wp-block-code
       [13-May-2026 11:11:48 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function is_checkout() in /home/sites/9b/e/e41a592f33/staging_html/wp-content/plugins/free-shipping-notification-woocommerce/public/class-cart-checkout-progress.php:254Stack trace:#0 /home/sites/......./staging_html/wp-includes/class-wp-hook.php(341): pisol_fsnw_cart_checkout_progress_bar->paymentScript('')#1 /home/sites/......./staging_html/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array)#2 /home/sites/......./staging_html/wp-includes/plugin.php(522): WP_Hook->do_action(Array)#3 /home/sites/......./staging_html/wp-includes/script-loader.php(2311): do_action('wp_enqueue_scri...')#4 /home/sites/......./staging_html/wp-includes/class-wp-hook.php(341): wp_enqueue_scripts('')#5 /home/sites/......./staging_html/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters(NULL, Array)#6 /home/sites/......./staging_html/wp-includes/plugin.php(522): WP_Hook->do_action(Array)#7 /home/sites/......./staging_html/wp-includes/general-template.php(3197): do_action('wp_head')#8 /home/sites/......./staging_html/wp-includes/template-canvas.php(17): wp_head()#9 /home/sites/......./staging_html/wp-includes/template-loader.php(132): include('/home/sites/9b/...')#10 /home/sites/......./staging_html/wp-blog-header.php(19): require_once('/home/sites/9b/...')#11 /home/sites/......./staging_html/index.php(17): require('/home/sites/9b/...')#12 {main}  thrown in /home/sites/......./staging_html/wp-content/plugins/free-shipping-notification-woocommerce/public/class-cart-checkout-progress.php on line 254
       ```
   
 * The PHP error is suggesting that the free-shipping-notification-woocommerce plugin
   is looking for WooCommerce – but it is deactivated with your plugin.
 * If I deactivate the free-shipping-notification-woocommerce plugin I don’t get
   a PHP error but still get the _WooCommerce plugin must be active for Address 
   Validation & Google Address Auto Complete Plugin for WooCommerce(Basic) to work_
   message. If I re-activate it and deactivate your plugin, all is well.
 * Any ideas please?
 * James
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fphp-fatal-error-502%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 6 replies - 1 through 6 (of 6 total)

 *  Plugin Author [Jose Mortellaro](https://wordpress.org/support/users/giuse/)
 * (@giuse)
 * [1 day, 11 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18907921)
 * Hi James,
 * thank you for reporting this issue.
 * Relevanssi  doesn’t check if the function is_checkout exists before using it.
   
   When a function is defined in another plugin you should always check if it exist
   before using that function. Unfortunately, some plugins don’t check it.
 * Probably, you deactivated WooCommerce somewhere, and those rules are applied 
   also during the searching process. Maybe Relevanssi calls the homepage, or another
   URL where that plugin is disabled. I don’t know. I should investigate it deeper
   to find out the main cause of this issue.
 * Anyway, I suggest update Freesoul Deactivate Plugins to the latest version v.
   2.6.2 and let me know if you still have the same issue.
 * Now FDP provides the function is_checkout when WooCommerce is disabled and you
   should not have any more the issue. But if you still ahve problems with version
   2.6.2, don’t hesitate to reply.
 * Best regards
 * Jose
 *  Thread Starter [James](https://wordpress.org/support/users/james-feaver/)
 * (@james-feaver)
 * [1 day, 11 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18907965)
 * Hi Jose,
 * Thanks for the swift action and response. I have updated your plugin on my staging
   site and still get exactly the same error – the Debug.log error is identical.
   I know I mentioned several different plugins including Relevanssi but note the
   plugin specifically mentioned in the error is the free-shipping-notification-
   woocommerce plugin ([https://en-gb.wordpress.org/plugins/free-shipping-notification-woocommerce/](https://en-gb.wordpress.org/plugins/free-shipping-notification-woocommerce/)).
 *     ```wp-block-code
       [14-May-2026 12:56:50 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function is_cart() in /home/sites/9b/e/e41a592f33/staging_html/wp-content/plugins/free-shipping-notification-woocommerce/public/class-cart-checkout-progress.php:254....
       ```
   
 * WooCommerce is enabled on every page of the site (so users can use it’s minicart
   from anywhere).
 * Thanks,
 * James
 *  Plugin Author [Jose Mortellaro](https://wordpress.org/support/users/giuse/)
 * (@giuse)
 * [1 day, 8 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18908172)
 * Hi James,
 * you are welcome! Before the fatal error was caused byt the missing function is_checkout.
   Now it’s caused by the missing function is_cart.
   Sorry, I didn’t check carefully
   the code of free-shipping-notification-woocommerce.I suggest download and test
   version 2.6.3 from this link: [https://downloads.wordpress.org/plugin/freesoul-deactivate-plugins.2.6.3.zip](https://downloads.wordpress.org/plugin/freesoul-deactivate-plugins.2.6.3.zip).
 * If the issue is solve with v. 2.6.3 I will publish it.
 * Best regards
 * Jose
 *  Thread Starter [James](https://wordpress.org/support/users/james-feaver/)
 * (@james-feaver)
 * [1 day, 8 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18908188)
 * Hi Jose,
 * A different error:
 *     ```wp-block-code
       Uncaught Error: Call to undefined function WC()in /home/sites/9b/e/e41a592f33/staging_html/wp-content/plugins/free-shipping-notification-woocommerce/includes/class-pisol-fsnw-shippingzone.php on line 62
       ```
   
 * Thanks,
 * James
 *  Plugin Author [Jose Mortellaro](https://wordpress.org/support/users/giuse/)
 * (@giuse)
 * [1 day, 6 hours ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18908259)
 * Hi James,
 * Unfortunately, FDP can’t replicate the function `WC()`.
 * It looks like **free-shipping-notification-woocommerce** doesn’t check whether
   a function exists before using it.
 * If you have the PRO version of FDP, you can solve this using the Plugin Dependencies
   settings. You can read more details here:
   [https://freesoul-deactivate-plugins.com/how-deactivate-plugins-on-specific-pages/keeping-plugins-always-active-when-another-plugin-is-active/](https://freesoul-deactivate-plugins.com/how-deactivate-plugins-on-specific-pages/keeping-plugins-always-active-when-another-plugin-is-active/)
 * If you only have the free version, I see three possible options:
    1. Contact the authors of **free-shipping-notification-woocommerce** and report
       this issue. You could tell them that when using a function that isn’t defined
       in their code and isn’t a native PHP function, they should first check whether
       the function exists.
    2. Carefully review your FDP settings. Try to identify where WooCommerce may be
       disabled while **free-shipping-notification-woocommerce** is still active. You
       mentioned that all plugins are enabled, but that might not actually be the case.
       To be sure, I suggest resetting the FDP settings.
       Be aware that you will lose
       all the FDP setttings.More details here:[https://freesoul-deactivate-plugins.com/how-deactivate-plugins-on-specific-pages/reset-fdp-settings/](https://freesoul-deactivate-plugins.com/how-deactivate-plugins-on-specific-pages/reset-fdp-settings/)
    3. Wait until I test Relevanssi and Free Shipping Bar for WooCommerce in my testing
       installation. At the moment, I can’t say how long this will take.
 * Best regards
 * Jose
 *  Thread Starter [James](https://wordpress.org/support/users/james-feaver/)
 * (@james-feaver)
 * [12 hours, 5 minutes ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18908970)
 * Hi Jose,
 * Thanks very much for the suggestions and your help. I reset the FDP settings,
   re-added the settings afresh and … all working as expected – no error when searching!
 * I’ll give you a 5* review after lunch.
 * Thanks,
 * James

Viewing 6 replies - 1 through 6 (of 6 total)

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 * 6 replies
 * 2 participants
 * Last reply from: [James](https://wordpress.org/support/users/james-feaver/)
 * Last activity: [12 hours, 5 minutes ago](https://wordpress.org/support/topic/php-fatal-error-502/#post-18908970)
 * Status: resolved