Generic function to return an array of posts formatted for CMB2. Simply pass in your WP_Query arguments and get back a beautifully formatted CMB2 options array.

functions.php

<?php
/**
 * Get a list of posts
 *
 * Generic function to return an array of posts formatted for CMB2. Simply pass
 * in your WP_Query arguments and get back a beautifully formatted CMB2 options
 * array.
 *
 * @param array $query_args WP_Query arguments
 * @return array CMB2 options array
 */
function iweb_get_cmb_options_array( $query_args ) {
	$defaults = array(
		'posts_per_page' => -1
	);

	$args = wp_parse_args( $query_args, $defaults );

	$query = new WP_Query( $args );

	$posts_array = array();

	if ( $query->have_posts() ) {
		while ( $query->have_posts() ) {
			$query->the_post();

			$posts_array[get_the_ID()] = get_the_title();
		}
	}

	wp_reset_postdata();

	return $posts_array;
}