Convert Mai Theme v1 banner images to v2 page header images.

mai-banner-to-page-header.php

<?php

/**
 * Migrates post and term meta keys from Mai Theme v1 to v2.
 * 
 * 1. Add this code to functions.php
 * 2. Visit the front end of the website ONE time.
 * 3. This code will run just by visiting the page.
 * 4. Each page view or refresh will make it run again so don't do it more than once.
 * 5. Immediate remove this code.
 * 6. Check your banner image fields to make sure the images are there.
 * 
 * @return void
 */
add_action( 'genesis_before_loop', function() {
	
	/**
	 * Migrate post meta keys from Mai Theme v1 to v2.
	 */
	$query = new WP_Query(
		[
			'post_type'              => 'post',
			'posts_per_page'         => 500,
			'offset'                 => 0,
			'post_status'            => 'any',
			'no_found_rows'          => true,
			'update_post_meta_cache' => false,
			'update_post_term_cache' => false,
		]
	);

	if ( $query->have_posts() ) {
		while ( $query->have_posts() ) : $query->the_post();
			$banner_id = get_post_meta( get_the_ID(), 'banner_id', true );

			if ( $banner_id ) {
				update_post_meta( get_the_ID(), 'page_header_image', $banner_id );
			}
		endwhile;
	}
	wp_reset_postdata();


	/**
	 * Migrate term meta keys from Mai Theme v1 to v2.
	 */
	$term_query = new WP_Term_Query(
		[
			'number'   => 500,
			'offset'   => 0,
			'taxonomy' => [
				'category',
				'post_tag',
			],
		]
	);

	if ( ! empty( $term_query->terms ) ) {

		/**
		 * Terms.
		 *
		 * @var WP_Term $term Term object.
		 */
		foreach ( $term_query->terms as $term ) {
			$banner_id = get_term_meta( $term->term_id, 'banner_id', true );

			if ( $banner_id ) {
				update_term_meta( $term->term_id, 'page_header_image', $banner_id );
			}
		}
	}	
});