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Troubleshooting Common CMB2 Multicheck Field Issues: Saving, Defaults, and Limits

16 threads Sep 10, 2025 Plugin → Cmb2

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CMB2's multicheck and multicheck_inline fields are powerful tools for creating complex WordPress options pages and meta boxes. However, users often encounter a specific set of problems that can be frustrating to debug. Based on community reports, this guide covers the most common multicheck field issues and their solutions.

1. Checkboxes Not Saving Correctly or Re-checking Themselves

The Problem: A user unchecks a box, saves the form, but the checkbox remains checked upon reload. The database may not reflect the change. This issue is particularly prevalent when multiple multicheck fields are used on an options page or when they are the last field in a configuration.

The Cause: This behavior is often related to how the form is structured and processed. A common thread in the community suggests that if there is no subsequent field after a multicheck, the saving mechanism can sometimes fail to properly register the "unchecked" state.

The Solution: A simple workaround reported by users is to add another field (like a text field) after the problematic multicheck field. This seems to ensure the form data is processed correctly. If you are using an options page, ensure your configuration is sound.

2. Setting Default Values for Multicheck Fields

The Problem: Users want to pre-select specific options in a multicheck field using the default_cb parameter, but the callback function does not execute.

The Cause: The default_cb parameter may not be the intended method for setting defaults on a multicheck field, which expects an array of default values, not a single value.

The Solution: For multicheck fields, use the 'default' parameter with an array of the keys you want to be checked by default. For example:

'default' => array( 'monday', 'tuesday' ),

If you need dynamic defaults, you must build this array within your callback and pass it to the 'default' parameter directly, not through default_cb.

3. Storing Keys Instead of Values

The Problem: The multicheck field saves the option keys (e.g., 'cherry_red') to the database in a serialized array instead of the human-readable values (e.g., 'Cherry Red').

The Cause: This is the intended behavior. CMB2 is designed to store the keys from the options array. The keys are the unique identifiers, while the values are for display purposes only.

The Solution: To display the values on the front end, you must use the saved key to look up the corresponding value from your original options array. When you retrieve the meta data, you will get an array of keys. Use a loop to get the friendly names:

$saved_colors = get_post_meta( $post_id, '_pc_quote_apparel_apparel_colors', true );
if ( ! empty( $saved_colors ) ) {
    $options = array( 'Cherry Red ' => 'Cherry Red ', 'Irish Green ' => 'Irish Green ', ... );
    foreach ( $saved_colors as $key ) {
        echo $options[ $key ] . '<br>';
    }
}

4. Apparent Limits on the Number of Checkboxes

The Problem: When a user selects a large number of options (e.g., all 27 in a list), the save operation fails, and the checkboxes appear unchecked.

The Cause: There is no hard-coded limit in CMB2 itself. The issue is likely related to server constraints, such as the max_input_vars PHP setting or issues with how serialized data is handled.

The Solution: Increase the max_input_vars value in your php.ini file. A large number of checkboxes can generate many input fields, potentially exceeding the default limit. Also, ensure there are no conflicts with other plugins or themes that might be corrupting the serialized data during save.

5. Select All / Deselect All Button Bug in Groups

The Problem: When using multicheck fields inside repeatable groups, the "Select All / Deselect All" button for one group affects all multicheck fields in every group.

The Cause: This is a known bug where the JavaScript for the buttons does not properly scope itself to its own group.

The Solution: The CMB2 team is aware of this issue. The recommended course of action is to disable the select all button by setting 'select_all_button' => false in your field configuration until a fix is released in a future version of the plugin.

Most issues with CMB2 multicheck fields stem from understanding their intended behavior and configuration. When in doubt, always review your field configuration code and check the official CMB2 wiki for guidance.

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