Low stock notification per product (adding custom fields)

low-stock-notification-custom-fields.php

<?php
/**
 * Custom product field to set low stock threshold
 * Requires WooCommerce 3.0
 */
function sp_custom_product_stock_threshold_field() {

	global $post;

	woocommerce_wp_text_input( array(
		'id'                => '_low_stock_threshold',
		'label'             => __( 'Low stock threshold', 'textdomain' ),
		'desc_tip'          => true,
		'description'       => __( 'Set the low stock threshold for this product', 'textdomain' ),
		'type'              => 'number',
		'default'           => get_option( 'woocommerce_notify_low_stock_amount' ), // Default to global
		'custom_attributes' => array(
			'step' => 'any'
		),
		'data_type'         => 'stock'
	) );


}
add_action( 'woocommerce_product_options_stock_fields', 'sp_custom_product_stock_threshold_field' );

/**
 * Save the custom fields.
 */
function sp_save_custom_product_inventory_settings( $post_id ) {

	if ( isset( $_POST['_low_stock_threshold'] ) ) :
		update_post_meta( $post_id, '_low_stock_threshold', absint( $_POST['_low_stock_threshold'] ) );
	endif;

}
add_action( 'woocommerce_process_product_meta', 'sp_save_custom_product_inventory_settings'  );


/**
 * Send custom low stock notifications per product
 * Requires WooCommerce 3.0
 *
 * @param WC_Order $order
 */
function sp_custom_low_stock_notification_improved_product_30( $order ) {

	foreach ( $order->get_items() as $item ) {
		if ( $item->is_type( 'line_item' ) && ( $product = $item->get_product() ) && $product->managing_stock() ) {
			$new_stock = $item->get_quantity();

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

			if ( ! empty( $low_stock_threshold ) && $new_stock < $low_stock_threshold ) {
				do_action( 'woocommerce_low_stock', $product );
			}
		}
	}

}
add_action( 'woocommerce_reduce_order_stock', 'sp_custom_low_stock_notification_improved_product_30', 10, 3 );