1function d_extra_product_field() {
 2   $value = isset( $_POST['extra_product_field'] ) ? htmlspecialchars( wp_kses_post( wp_unslash( $_POST['extra_product_field'] ) ), ENT_QUOTES, 'UTF-8' ) : '';
 3    $nonce = wp_create_nonce( 'd_extra_product_field_nonce' );
 4 
 5    echo '<div class="extra-product-field">';
 6    echo '<label for="extra_product_field">' . esc_html__( 'Add a note to the purchase:', 'domain' ) . '</label>';
 7        echo '<input type="text" id="extra_product_field" name="extra_product_field" value="' . esc_attr( $value ) . '" maxlength="500" />';
 8    echo '<input type="hidden" name="d_extra_product_field_nonce" value="' . esc_attr( $nonce ) . '" />';
 9    echo '</div>';
10}
11add_action( 'woocommerce_before_add_to_cart_button', 'd_extra_product_field', 9 );
12 
13function d_verify_extra_product_field_nonce() {
14    if ( ! isset( $_POST['d_extra_product_field_nonce'] ) ) {
15        return;
16    }
17 
18    if ( ! wp_verify_nonce( sanitize_key( $_POST['d_extra_product_field_nonce'] ), 'd_extra_product_field_nonce' ) ) {
19        wp_die( 'Security check failed' );
20    }
21}
22add_action( 'woocommerce_add_to_cart', 'd_verify_extra_product_field_nonce' );
23 
24 
25 
26function d_add_cart_item_data( $cart_item_data, $product_id ) {
27    if ( isset( $_POST['extra_product_field'] ) && isset( $_POST['d_extra_product_field_nonce'] ) && wp_verify_nonce( $_POST['d_extra_product_field_nonce'], 'd_extra_product_field_nonce' ) ) {
28        $cart_item_data['extra_product_field'] = wp_kses_post( $_POST['extra_product_field'] );
29    }
30    return $cart_item_data;
31}
32add_filter( 'woocommerce_add_cart_item_data', 'd_add_cart_item_data', 10, 2 );
33 
34function d_get_cart_item_from_session( $cart_item, $values ) {
35    if ( isset( $values['extra_product_field'] ) ) {
36        $cart_item['extra_product_field'] = $values['extra_product_field'];
37    }
38    return $cart_item;
39}
40add_filter( 'woocommerce_get_cart_item_from_session', 'd_get_cart_item_from_session', 20, 2 );
41 
42function d_add_order_item_meta( $item_id, $values ) {
43    if ( ! empty( $values['extra_product_field'] ) ) {
44        woocommerce_add_order_item_meta( $item_id, __('Note', 'domain'), $values['extra_product_field'] );
45    }
46}
47add_action( 'woocommerce_add_order_item_meta', 'd_add_order_item_meta', 10, 2 );
48 
49 
50function display_extra_product_field_in_order_view( $item_data, $cart_item ) {
51    if( isset( $cart_item['extra_product_field'] ) ){
52        $item_data[] = array(
53            'key' => esc_html__( 'Бележка', 'woocommerce' ),
54            'value' => sanitize_text_field( $cart_item['extra_product_field'] )
55        );
56    }
57    return $item_data;
58}
59 
60add_filter( 'woocommerce_get_item_data', 'display_extra_product_field_in_order_view', 10, 2 );
61 
62// add field data in email
63function d_order_email_data( $fields ) {
64    $fields['extra_product_field'] = esc_attr( __( 'extra_product_field' ) );
65    return $fields;
66}
67add_filter('woocommerce_email_order_meta_fields', 'd_order_email_data');