How to Autofill the Title of the cutstom post with the value of the 2 fields

Hello,

I have created this snippet (I don't want to change my function.php) with code snippet:

my metabox is fields-for-agent

add_action( 'rwmb_fields-for-agent_after_save_post', 'update_post_title' );

function update_post_title( $post_id ) {
    // Get the field value
    $t1 = rwmb_meta( 'first_name', '', $post_id );
    $t2 = rwmb_meta( 'last_name', '', $post_id );

    // Get the post title
    $my_post_title = get_the_title( $post_id );
    
    // Preprare update post
    $my_post = array(
        'ID' => $post_id,
        'post_title' => $t1 . ' ' . $t2,
        'post_name' => $t1 . '_' . $t2,
    );

    wp_update_post( $my_post );
}

But it does not work and I don't find why.

Maybe because the field "post_title" is in the metabox?

Thank you.

Here are the custom fields:

<?php
add_filter( 'rwmb_meta_boxes', 'your_prefix_function_name' );

function your_prefix_function_name( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = [
        'title'              => __( 'Fields for agent', 'your-text-domain' ),
        'id'                 => 'fields-for-agent',
        'post_types'         => ['agent'],
        'tab_style'          => 'box',
        'tab_default_active' => 'identity',
        'geo'                => [
            'api_key' => 'AIzaSyDdkC7vnU_nm-feorsOVR6FUWG_MCW3zzg',
        ],
        'tabs'               => [
            'identity'               => [
                'label' => 'Identity',
                'icon'  => 'admin-users',
            ],
            'location_and_languages' => [
                'label' => 'Location and Languages',
                'icon'  => 'admin-site',
            ],
            'your_offer'             => [
                'label' => 'Your offer',
                'icon'  => 'welcome-edit-page',
            ],
        ],
        'fields'             => [
            [
                'name'          => __( 'First name', 'your-text-domain' ),
                'id'            => $prefix . 'first_name_agent',
                'type'          => 'text',
                'admin_columns' => [
                    'position'   => 'after',
                    'sort'       => true,
                    'searchable' => true,
                    'filterable' => true,
                ],
                'columns'       => 6,
                'visible'       => [
                    'when'     => [['', '=', '']],
                    'relation' => 'or',
                ],
                'tab'           => 'identity',
            ],
            [
                'name'    => __( 'Last name', 'your-text-domain' ),
                'id'      => $prefix . 'last_name_agent',
                'type'    => 'text',
                'columns' => 6,
                'tab'     => 'identity',
            ],
            [
                'name'              => __( 'Photo', 'your-text-domain' ),
                'id'                => $prefix . '_thumbnail_id',
                'type'              => 'image',
                'label_description' => __( 'Photo which best promotes you', 'your-text-domain' ),
                'max_file_uploads'  => 1,
                'admin_columns'     => [
                    'position'   => 'before post_title',
                    'searchable' => true,
                ],
                'tab'               => 'identity',
            ],
            [
                'name'    => __( 'Company', 'your-text-domain' ),
                'id'      => $prefix . 'company_agent',
                'type'    => 'text',
                'columns' => 6,
                'tab'     => 'identity',
            ],
            [
                'name'    => __( 'Website', 'your-text-domain' ),
                'id'      => $prefix . 'website_agent',
                'type'    => 'url',
                'columns' => 6,
                'tab'     => 'identity',
            ],
            [
                'name'    => __( 'Email', 'your-text-domain' ),
                'id'      => $prefix . 'email_agent',
                'type'    => 'email',
                'columns' => 6,
                'tab'     => 'identity',
            ],
            [
                'name'    => __( 'Tel', 'your-text-domain' ),
                'id'      => $prefix . 'tel_agent',
                'type'    => 'tel',
                'columns' => 6,
                'tab'     => 'identity',
            ],
            [
                'name' => __( 'Address', 'your-text-domain' ),
                'id'   => $prefix . 'address_agent',
                'type' => 'text',
                'tab'  => 'location_and_languages',
            ],
            [
                'name'          => __( 'Country', 'your-text-domain' ),
                'id'            => $prefix . 'country_agent',
                'type'          => 'text',
                'binding'       => 'country',
                'address_field' => 'address_agent',
                'tab'           => 'location_and_languages',
            ],
            [
                'name'          => __( 'Map', 'your-text-domain' ),
                'id'            => $prefix . 'map_gm_agent',
                'type'          => 'map',
                'api_key'       => 'AIzaSyDdkC7vnU_nm-feorsOVR6FUWG_MCW3zzg',
                'address_field' => 'address_agent',
                'tab'           => 'location_and_languages',
            ],
            [
                'name'       => __( 'Language(s)', 'your-text-domain' ),
                'id'         => $prefix . 'languages',
                'type'       => 'taxonomy',
                'taxonomy'   => ['languages'],
                'field_type' => 'select_advanced',
                'add_new'    => true,
                'tab'        => 'location_and_languages',
            ],
            [
                'name'       => __( 'Countries of Operation', 'your-text-domain' ),
                'id'         => $prefix . 'countries_of_operation',
                'type'       => 'taxonomy',
                'taxonomy'   => ['country-of-operation'],
                'field_type' => 'select_advanced',
                'multiple'   => true,
                'add_new'    => true,
                'tab'        => 'location_and_languages',
            ],
            [
                'name' => __( 'Background', 'your-text-domain' ),
                'id'   => $prefix . 'background_agent',
                'type' => 'textarea',
                'rows' => 10,
                'tab'  => 'your_offer',
            ],
            [
                'name' => __( 'Services', 'your-text-domain' ),
                'id'   => $prefix . 'services_agent',
                'type' => 'textarea',
                'rows' => 10,
                'tab'  => 'your_offer',
            ],
            [
                'name' => __( 'References', 'your-text-domain' ),
                'id'   => $prefix . 'references',
                'type' => 'textarea',
                'rows' => 10,
                'tab'  => 'your_offer',
            ],
            [
                'name' => __( 'Video Presentation', 'your-text-domain' ),
                'id'   => $prefix . 'video_presentation_agent',
                'type' => 'url',
                'std'  => 'https://www.youtube.com/watch?v=ZRngEOnHnoc',
                'tab'  => 'your_offer',
            ],
        ],
    ];

    return $meta_boxes;
}

When the snippet is activated:

• WHen I save a post, the title becomes empty (no title) and the slug url (post_name) becomes "_"
• So it means that the snippet does something. And because the post_name only becomes "_", it means that $t1 and $t2 are empty.
  But I don't know why.

I found it by looking at the code!
in the snippet, I put last_name as variable instead of last_name_agent, the same with first_name.

It works! Thank you for your support!