Select Advanced std

<?php
function select_advanced( $meta_boxes ) {
    $prefix = 'prefix-';

    $meta_boxes[] = array(
        'id' => 'untitled',
        'title' => esc_html__( 'Untitled Metabox', 'metabox-online-generator' ),
        'post_types' => array('post', 'page' ),
        'context' => 'advanced',
        'priority' => 'default',
        'autosave' => 'false',
        'fields' => array(
            array(
                'id' => $prefix . 'select_advanced_1',
                'name' => esc_html__( 'Select Advanced', 'metabox-online-generator' ),
                'type' => 'select_advanced',
                'placeholder' => esc_html__( 'Select an Item', 'metabox-online-generator' ),
                'options'     => array(
                    'java'       => 'Java',
                    'javascript' => 'JavaScript',
                    'php'        => 'PHP',
                    'csharp'     => 'C#',
                    'objectivec' => 'Objective-C',
                    'kotlin'     => 'Kotlin',
                    'swift'      => 'Swift',
                ),
                'std' => 'swift',
            ),
        ),
    );

    return $meta_boxes;
}
add_filter( 'rwmb_meta_boxes', 'select_advanced' );