Title: PHP 8 Warning: Undefined array key “cacheStore” + minor code issues
Last modified: April 26, 2026

---

# PHP 8 Warning: Undefined array key “cacheStore” + minor code issues

 *  Resolved [aduwow](https://wordpress.org/support/users/aduwow/)
 * (@aduwow)
 * [1 month ago](https://wordpress.org/support/topic/php-8-warning-undefined-array-key-cachestore-minor-code-issues/)
 * Hello,
 * I’m using the WP-Appbox plugin and encountered a PHP 8 warning in the admin area:
 *     ```wp-block-code
       Warning: Undefined array key "cacheStore"
       ```
   
 * 📍 Location
 * The issue occurs in the following file:
 *     ```wp-block-code
       wp-appbox/admin/settings-cache-list.php
       ```
   
 * 🔍 Root cause
 * The warning is caused by accessing `$_POST['cacheStore']` without checking if
   the key exists.
 * Examples:
 *     ```wp-block-code
       selected( $_POST['cacheStore'], $storeID );
       ```
   
 * and:
 *     ```wp-block-code
       $this->fillData( sanitize_text_field( $_POST['cacheSearch'] ), sanitize_text_field( $_POST['cacheStore'] ) );
       ```
   
 * In PHP 8+, this triggers a warning when the form has not been submitted yet.✅
   Suggested fix
 * Use `isset()` or null coalescing to prevent undefined array key warnings:
 *     ```wp-block-code
       selected( $_POST['cacheStore'] ?? '', $storeID );
       ```
   
 * and:
 *     ```wp-block-code
       $search = isset($_POST['cacheSearch']) ? sanitize_text_field($_POST['cacheSearch']) : '';
       $store  = isset($_POST['cacheStore']) ? sanitize_text_field($_POST['cacheStore']) : '';
   
       $this->fillData($search, $store);
       ```
   
 * ⚠️ Additional issue
 * There is also a syntax issue in the same file:
 *     ```wp-block-code
       else( false );
       ```
   
 * This should be:
 *     ```wp-block-code
       else return false;
       ```
   
 * Please consider updating the plugin for PHP 8 compatibility.
 * Thanks!

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 * 0 replies
 * 1 participant
 * Last reply from: [aduwow](https://wordpress.org/support/users/aduwow/)
 * Last activity: [1 month ago](https://wordpress.org/support/topic/php-8-warning-undefined-array-key-cachestore-minor-code-issues/)
 * Status: resolved