Blocksy Change Product Card Swap Image With Custom Field

blc-2-change-product-hover-image.php

<?php
add_filter(
	'blocksy:woocommerce:product-card:thumbnail:gallery-images',
	function ($gallery_images) {
		if (! is_product() && ! is_shop() && ! is_product_category()) {
			return $gallery_images;
		}

		global $product;

		if (! $product) {
			return $gallery_images;
		}

		$hover_image_url = get_post_meta(
			$product->get_id(),
			'hover_image_url',
			true
		);

		if (! $hover_image_url) {
			return $gallery_images;
		}

		// Keep main image, inject hover image as second
		return array_merge(
			[$gallery_images[0]],
			[
				[
					'url' => esc_url($hover_image_url)
				]
			]
		);
	},
	20
);