Custom checkout field validation on Woocommerce - php

Question

My code:
add_action( 'woocommerce_before_checkout_form', 'fruit_field' );
function fruit_field( $checkout ) {
woocommerce_form_field( 'fruit', array(
'type' => 'select',
'required' => true,
'options' => array(
'apple' => __('Apple'),
'banana' => __('Banana'),
'watermelon' => __('Watermelon'),
'other' => __('Other'),
),
'class' => array('my-class'),
'label' => __('Best fruit?'),
), $checkout->get_value( 'fruit' ));
}
And the validation:
add_action('woocommerce_checkout_process', 'process_checkout');
function process_checkout() {
if ($_POST['fruit'] === null) {
wc_add_notice( __( 'No fruits?' ), 'error' );
}
}
After submitting the form, it always displays my custom error "No fruits?", no matter what was selected. Is $_POST['fruit'] somehow not available in the process_checkout function?

Answer 1

You can not use custom checkout fields in woocommerce_before_checkout_form hook as your field is outside the checkout form, and it is not posted on submit.
Instead you should use woocommerce_checkout_before_customer_details action hook instead:
add_action( 'woocommerce_checkout_before_customer_details', 'fruit_custom_checkout_field' );
function fruit_custom_checkout_field() {
woocommerce_form_field( '_fruit', array(
'type' => 'select',
'label' => __('Best fruit?'),
'class' => array('my-fruit'),
'required' => true,
'options' => array(
'' => __('Chose a fruit'),
'Apple' => __('Apple'),
'Banana' => __('Banana'),
'Watermelon' => __('Watermelon'),
'Other' => __('Other'),
),
), WC()->checkout->get_value('_fruit') );
}
add_action('woocommerce_checkout_process', 'process_fruit_custom_checkout_field');
function process_fruit_custom_checkout_field() {
if (isset($_POST['_fruit']) && empty($_POST['_fruit']) ) {
wc_add_notice( __( 'please choose a "fruits"' ), 'error' );
}
}
// Save the custom checkout field in the order meta
add_action( 'woocommerce_checkout_create_order', 'save_fruit_custom_field_as_meta_data', 10, 2 );
function save_fruit_custom_field_as_meta_data( $order, $data ) {
if (isset($_POST['_fruit']) && ! empty($_POST['_fruit']) ) {
$order->update_meta_data('_custom_field', esc_attr( $_POST['_fruit'] ) );
}
}
Code goes in function.php file of your active child theme (or active theme). Tested and works.