Title: PHP Warning: Undefined array key “_zaddon_additional”
Last modified: April 1, 2022

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# PHP Warning: Undefined array key “_zaddon_additional”

 *  [isarisar](https://wordpress.org/support/users/isarisar/)
 * (@isarisar)
 * [4 years, 2 months ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/)
 * Hi,
 * a warning keeps popping up in our log:
 * `PHP Warning: Undefined array key "_zaddon_additional" in /srv/wp-content/plugins/
   product-add-ons-woocommerce/includes/Frontend/Product.php on line 357`

Viewing 4 replies - 1 through 4 (of 4 total)

 *  Thread Starter [isarisar](https://wordpress.org/support/users/isarisar/)
 * (@isarisar)
 * [4 years, 2 months ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/#post-15517689)
 * Version info:
    PAOfWC: 2.1.38 WC 6.3.1 WP 5.9.2 PHP 8.0.17
 *  Thread Starter [isarisar](https://wordpress.org/support/users/isarisar/)
 * (@isarisar)
 * [4 years, 2 months ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/#post-15519770)
 * Another unrelated, but this time critical error I’ve found in the log:
 *     ```
       CRITICAL Uncaught Error: Call to a member function get_category_ids() on bool in /srv/wp-content/plugins/product-add-ons-woocommerce/includes/Model/Group.php:344
       Stack trace:
       #0 /srv/wp-content/plugins/product-add-ons-woocommerce/includes/Frontend/Product.php(521): ZAddons\Model\Group::getByProduct()
       #1 /srv/wp-includes/class-wp-hook.php(309): ZAddons\Frontend\Product->add_to_cart_validation()
       #2 /srv/wp-includes/plugin.php(189): WP_Hook->apply_filters()
       #3 /srv/wp-content/plugins/woocommerce/includes/class-wc-form-handler.php(904): apply_filters()
       #4 /srv/wp-content/plugins/woocommerce/includes/class-wc-form-handler.php(790): WC_Form_Handler::add_to_cart_handler_variable()
       #5 /srv/wp-includes/class-wp-hook.php(307): WC_Form_Handler::add_to_cart_action()
       #6 /srv/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
       #7 /srv/wp-includes/plugin.php(474): WP_Hook->do_action()
       #8 /srv/wp-settings.php(609): do_action()
       #9 /srv/wp-config.php(128): require_once('...')
       #10 /srv/wp-load.php(50): require_once('...')
       #11 /srv/wp-blog-header.php(13): require_once('...')
       #12 /srv/index.php(17): require('...')
       #13 {main}
         thrown in /srv/wp-content/plugins/product-add-ons-woocommerce/includes/Model/Group.php in line 344
       ```
   
 *  Thread Starter [isarisar](https://wordpress.org/support/users/isarisar/)
 * (@isarisar)
 * [4 years, 1 month ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/#post-15540051)
 * Any response?
 * I checked a bit more, and it can actually be two warnings about faulty accesses:
 * > PHP Warning: Undefined array key “_zaddon_additional” in /srv/wp-content/plugins/
   > product-add-ons-woocommerce/includes/Frontend/Product.php on line 357
   >  PHP 
   > Warning: Undefined array key “_zaddon_additional” in /srv/wp-content/plugins/
   > product-add-ons-woocommerce/includes/Frontend/Product.php on line 272
 * That’s `$cart_item['_zaddon_additional'] = $values['_zaddon_additional']` and`
   $cart_item['_zaddon_additional'] > 0` respectively.
 * Both of them seem (at least) related to certain products being added to the cart,
   and then each time the cart site is opened.
 *  Thread Starter [isarisar](https://wordpress.org/support/users/isarisar/)
 * (@isarisar)
 * [4 years, 1 month ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/#post-15541871)
 * Another:
 * > PHP Warning: Undefined array key “_zaddon_additional” in /srv/wp-content/plugins/
   > product-add-ons-woocommerce/includes/Frontend/Product.php on line 227

Viewing 4 replies - 1 through 4 (of 4 total)

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 * 4 replies
 * 1 participant
 * Last reply from: [isarisar](https://wordpress.org/support/users/isarisar/)
 * Last activity: [4 years, 1 month ago](https://wordpress.org/support/topic/php-warning-undefined-array-key-_zaddon_additional/#post-15541871)
 * Status: not resolved