Custom field in media library not saving, selected() function not adding “selected” to select list input type

Following the approach in the developer docs for selected() but can’t get it to work with a custom field in the media library for a select list.

It won’t save the value, or become “selected”. Looks like WP is doing some js/ajax in the background here, so do I need to approach this differently or have a dumb typo?

Please see code below, help is appreciated.

/*
Add license field to media attachments 
*/

    function add_custom_field_license( $form_fields, $post ) {
        $license_field = get_post_meta($post->ID, 'license_field');
        $form_fields['license_field'] = [
            'label' => 'License',
            'input' => 'html',
            'html' => "<select name='attachments[{$post->ID}][license_field]' id='attachments-{$post->ID}-license_field'> 
        <option value='none' " . selected($license_field, "none") . ">None (all rights reserved)</option>
        <option value='CC0' " . selected($license_field, "CC0") . ">CC0</option>
        <option value='CC BY' " . selected($license_field, "CC BY") . ">CC BY</option>
        </select>",
        ];
        return $form_fields;
    }
    add_filter('attachment_fields_to_edit', 'add_custom_field_license', null, 2); 



/*
Save license field to media attachments
*/
function save_custom_field_license($post, $attachment) {  
    if( isset($attachment['license_field']) ){  
        update_post_meta($post['ID'], 'license_field', sanitize_text_field( $attachment['license_field'] ) );  
    }else{
         delete_post_meta($post['ID'], 'license_field' );
    }
    return $post;  
}
add_filter('attachment_fields_to_save', 'save_custom_field_licenser', null, 2);

Answers:

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Method 1

As per outlined in the comments, by fixing a typo in my save function, and setting the third parameter in get_post_meta() to true, and false in selected() it worked liked a charm. Thanks everyone!

Here’s the working code in case anyone is trying to add a select list custom field to their media manager:

   /*
    Add license field to media attachments 
    */
    
    function add_custom_field_license( $form_fields, $post ) {
        $license_field = get_post_meta($post->ID, 'license_field', true);
        $form_fields['license_field'] = [
            'label' => 'License',
            'input' => 'html',
            'html' => "<select name='attachments[{$post->ID}][license_field]' id='attachments-{$post->ID}-license_field'> 
        <option value='none' " . selected($license_field, "none", false) . ">None (all rights reserved)</option>
        <option value='CC0' " . selected($license_field, "CC0", false) . ">CC0</option>
        <option value='CC BY' " . selected($license_field, "CC BY", false) . ">CC BY</option>
        <option value='CC BY-NC' " . selected($license_field, "CC BY-NC", false) . ">CC BY-NC</option>
        <option value='CC BY-SA' " . selected($license_field, "CC BY-SA", false) . ">CC BY-SA</option>
        <option value='CC BY-NC-ND' " . selected($license_field, "CC BY-NC-ND", false) . ">CC BY-NC-ND</option>
        </select>",
        ];
        return $form_fields;
    }
    add_filter('attachment_fields_to_edit', 'add_custom_field_license', null, 2); 
     
    /*
    Save license field to media attachments
    */

    function save_custom_field_license($post, $attachment) {  
        if( isset($attachment['license_field']) ){  
            update_post_meta($post['ID'], 'license_field', sanitize_text_field( $attachment['license_field'] ) );  
        }else{
             delete_post_meta($post['ID'], 'license_field' );
        }
        return $post;  
    }
    add_filter('attachment_fields_to_save', 'save_custom_field_license', null, 2);

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0