Add Product Category to email subject WooCommerce

prod_cat_email.php

<?php
add_filter( 'woocommerce_email_subject_new_order', 'customizing_new_order_subject', 10, 2 );
function customizing_new_order_subject( $formated_subject, $order ) {

	$email              = WC()->mailer->get_emails()['WC_Email_New_Order'];
	$subject            = $email->get_option( 'subject', $email->get_default_subject() );
	$product_categories = array();

	foreach ( $order->get_items() as $item ) {
		$product_categories[] = implode( ', ', wp_get_post_terms( $item->get_product_id(), 'product_cat', array( 'fields' => 'names' ) ) );
	}

	$categories_string = implode( ', ', $product_categories );
	$subject           = str_replace( '{product_category}', $categories_string, $subject );

	return $email->format_string( $subject );
}