wordpress-plugin-woocommerce-purchase-order.php

<?php
/*
Plugin Name: WooCommerce Checkout Purchase Order Field
Version: 1.0
Description: Adds a purchase order field to the checkout.
Author: Nick Breen
Author URI: http://foobar.net.nz
Plugin URI: https://github.com/nickbreen/wordpress-plugin-woocommerce-purchase-order
*/

// Our new fields.
$fields = array(
    'purchase_order_reference' => array(
        'type' => 'text', //type of field (text, textarea, password, select)
        'label' => 'Purchase Order Reference', //label for the input field
        // 'placeholder' => '', //placeholder for the input
        // 'class' => '', //class for the input
        // 'required' => false, //true or false, whether or not the field is require
        // 'clear' => false, //true or false, applies a clear fix to the field/label
        // 'label_class' => '', //class for the label element
        // 'options' => '', //for select boxes, array of options (key => value pairs)
    ),
);

// We'll put out new fields into the checkout form's $form section
$form = 'order';
$form_fields = array(
    $form => $fields,
);

// Label for the admin edit order section
$order_details_label = 'Order Details';

// Validation filters for our new fields.
$field_filters = array(
    'purchase_order_reference' => array(
        'filter' => FILTER_CALLBACK,
        'flags' => FILTER_REQUIRE_SCALAR,
        'options' => function ($value) {
            // if the string does not contain anything unusual
            return filter_var($value, FILTER_SANITIZE_STRING) === $value ? $value : false;
        },
        'notice' => sprintf('<strong>%s</strong> is invalid.', $fields['purchase_order_reference']['label']),
    ),
);

add_filter('woocommerce_checkout_fields', function ($fields) use ($form_fields) {
    return array_merge_recursive($fields, $form_fields);
});

add_action('woocommerce_checkout_process', function () use ($field_filters) {
    $filtered_fields = filter_input_array(INPUT_POST, $field_filters, true);
    foreach ($filtered_fields as $field => $result) {
        // $result === NULL if unspecified, which is OK
        if (false === $result) { // if filter failed, which is not OK
            wc_add_notice($field_filters[$field]['notice'], 'error');
        }
    }
});

add_action('woocommerce_checkout_update_order_meta', function ($order_id) use ($fields, $field_filters) {
    $filtered_fields = filter_input_array(INPUT_POST, $field_filters, true);
    foreach ($filtered_fields as $field => $result) {
        if (false !== $result &&  null !== $result) {
            update_post_meta($order_id, $field, $result);
        }
    }
});

add_filter('woocommerce_email_order_meta_fields', function ($email_fields, $sent_to_admin, $order) use ($fields) {
    foreach ($fields as $field => $def) {
        $email_fields[] = array(
            'label' => $def['label'],
            'value' => get_post_meta($order->id, $field, true),
        );
    }

    return $email_fields;
}, 10, 3);

add_action('woocommerce_admin_order_data_after_order_details', function ($order) use ($fields, $order_details_label) {
    foreach ($fields as $field => $def) {
        if ($value = get_post_meta($order->id, $field, true)) {
            $s .= sprintf(
                '<p class="form-field form-field-wide"><label for="%1$s">%2$s:</label>'.
                '<input type="text" id="%1$s" value="%3$s" readonly/></p>',
                esc_attr($field),
                esc_html($def['label']),
                esc_attr($value)
            );
        }
    }
    if ($s) {
        printf(
            '<div class="clear"></div>'.
            '<h4 style="clear: both">%s</h4>'.
            '<div class="address">%s</div>',
            $order_details_label,
            $s
        );
    }
});

add_action('woocommerce_thankyou', function ($order_id) use ($fields) {
    foreach ($fields as $field => $def) {
        if ($value = get_post_meta($order_id, $field, true)) {
            $s .= sprintf('<tr><th>%s:</th><td>%s<td/></tr>', esc_html($def['label']), esc_html($value));
        }
    }
    if ($s) {
        printf('<table class="shop_table order_details">%s</table>', $s);
    }
}, 5);

// Also add the field to the PDF invoice/packing-slip if the plugin is available.
// See http://docs.wpovernight.com/woocommerce-pdf-invoices-packing-slips/pdf-template-action-hooks/
add_action('wpo_wcpdf_after_order_data', function ($template_type, $order) use ($fields) {
    foreach ($fields as $field => $def) {
        if ($value = get_post_meta($order->id, $field, true)) {
            printf('<tr><th>%s:</th><td>%s<td/></tr>', esc_html($def['label']), esc_html($value));
        }
    }
}, 10, 2);

add_action('wpo_wcpdf_before_item_meta', function ($template_type, $item, $order) {
    printf(
        '<span class="item-meta"><dl><dt>%s:</dt><dd><p>%s</p></dd></dl></span>',
        'Unit Price',
        $item['ex_single_price']
    );
}, 10, 3);