Custom product field

<?php

// ZS
/**
 * Adding Custom EAN Meta Field
 * Save meta data to DB
 */
// add EAN input field
add_action('woocommerce_product_options_inventory_product_data', 'woocom_simple_product_ean_field', 10, 1);
function woocom_simple_product_ean_field()
{
	global $woocommerce, $post;
	$product = new WC_Product(get_the_ID());
	echo '<div id="ean_attr" class="options_group">';
	//add EAN field for simple product
	woocommerce_wp_text_input(
		array(
		'id'             => '_ean',
		'label'           => __('EAN', 'zomerspecialist'),
		'placeholder'     => '01234567891231',
		'desc_tip'        => 'true',
		'description'     => __('Voer hier de EAN code in', 'zomerspecialist')
		)
	);
	echo '</div>';
}
// save simple product EAN
add_action('woocommerce_process_product_meta', 'woocom_simple_product_ean_save');
function woocom_simple_product_ean_save($post_id)
{
	$ean_post = $_POST['_ean'];
	// save the EAN
	if (isset($ean_post)) {
		update_post_meta($post_id, '_ean', esc_attr($ean_post));
	}
	// remove if EAN meta is empty
	$ean_data = get_post_meta($post_id, '_ean', true);
	if (empty($ean_data)) {
		delete_post_meta($post_id, '_ean', '');
	}
}



// Add Variation EAN Meta Field
add_action('woocommerce_product_after_variable_attributes', 'variation_settings_fields', 10, 3);
function variation_settings_fields($loop, $variation_data, $variation)
{
	// Text Field
	woocommerce_wp_text_input(
		array(
		'id'          => '_ean[' . $variation->ID . ']',
		'label'           => __('ean', 'textdomain'),
		'placeholder'     => '01234567891231',
		'desc_tip'    => 'true',
		'description'     => __('Voer hier de EAN code in', 'zomerspecialist'),
		'value'       => get_post_meta($variation->ID, '_ean', true)
		)
	);
}
// Save Variation EAN Meta Field Settings
add_action('woocommerce_save_product_variation', 'save_variation_settings_fields', 10, 2);
function save_variation_settings_fields($post_id)
{

	$ean_post = $_POST['_ean'][ $post_id ];
	// save the EAN
	if (isset($ean_post)) {
		update_post_meta($post_id, '_ean', esc_attr($ean_post));
	}
	// remove if EAN meta is empty
	$ean_data = get_post_meta($post_id, '_ean', true);
	if (empty($ean_data)) {
		delete_post_meta($post_id, '_ean', '');
	}
}