Add Custom Field to WooCommerce Checkout Page

/**
 * Add custom fields to WooCommerce checkout page
 * Easily add text, select, checkbox, or textarea fields to checkout
 * Prefix: tpsc_ (TP Snippet Collection)
 */

// ============================================
// CONFIGURATION - Customize your fields here
// ============================================

// Define your custom fields
function tpsc_get_custom_checkout_fields() {
    return array(
        // Example Field 1: VAT/Tax ID Number
        'vat_number' => array(
            'type'        => 'text',
            'label'       => __('VAT/Tax ID Number', 'woocommerce'),
            'placeholder' => __('Enter your VAT number', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 25,
            'section'     => 'billing', // billing, shipping, or order
        ),
        
        // Example Field 2: Delivery Instructions
        'delivery_instructions' => array(
            'type'        => 'textarea',
            'label'       => __('Delivery Instructions', 'woocommerce'),
            'placeholder' => __('Special delivery instructions...', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 100,
            'section'     => 'order',
        ),
        
        // Example Field 3: How did you hear about us?
        'referral_source' => array(
            'type'        => 'select',
            'label'       => __('How did you hear about us?', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 110,
            'section'     => 'order',
            'options'     => array(
                ''          => __('Please select...', 'woocommerce'),
                'google'    => __('Google Search', 'woocommerce'),
                'facebook'  => __('Facebook', 'woocommerce'),
                'instagram' => __('Instagram', 'woocommerce'),
                'friend'    => __('Friend/Family', 'woocommerce'),
                'other'     => __('Other', 'woocommerce'),
            ),
        ),
        
        // Example Field 4: Gift Message
        'is_gift' => array(
            'type'        => 'checkbox',
            'label'       => __('This is a gift', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 120,
            'section'     => 'order',
        ),
        
        'gift_message' => array(
            'type'        => 'textarea',
            'label'       => __('Gift Message', 'woocommerce'),
            'placeholder' => __('Enter your gift message here...', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 121,
            'section'     => 'order',
            'conditional' => 'is_gift', // Show only if is_gift is checked
        ),
        
        // Example Field 5: Company Registration Number
        'company_reg_number' => array(
            'type'        => 'text',
            'label'       => __('Company Registration Number', 'woocommerce'),
            'placeholder' => __('Enter registration number', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 26,
            'section'     => 'billing',
        ),
        
        // Example Field 6: Preferred Delivery Date
        'preferred_delivery_date' => array(
            'type'        => 'date',
            'label'       => __('Preferred Delivery Date', 'woocommerce'),
            'required'    => false,
            'class'       => array('form-row-wide'),
            'priority'    => 130,
            'section'     => 'order',
            'custom_attributes' => array(
                'min' => date('Y-m-d', strtotime('+1 day')),
                'max' => date('Y-m-d', strtotime('+30 days')),
            ),
        ),
    );
}

// ============================================
// ADD FIELDS TO CHECKOUT
// ============================================

// Add fields to billing section
add_filter('woocommerce_billing_fields', 'tpsc_add_billing_fields');
function tpsc_add_billing_fields($fields) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        if ($field['section'] === 'billing') {
            $fields['billing_' . $key] = $field;
        }
    }
    
    return $fields;
}

// Add fields to shipping section
add_filter('woocommerce_shipping_fields', 'tpsc_add_shipping_fields');
function tpsc_add_shipping_fields($fields) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        if ($field['section'] === 'shipping') {
            $fields['shipping_' . $key] = $field;
        }
    }
    
    return $fields;
}

// Add fields to order notes section
add_filter('woocommerce_checkout_fields', 'tpsc_add_order_fields');
function tpsc_add_order_fields($fields) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        if ($field['section'] === 'order') {
            $fields['order'][$key] = $field;
        }
    }
    
    return $fields;
}

// ============================================
// VALIDATE FIELDS
// ============================================

add_action('woocommerce_checkout_process', 'tpsc_validate_custom_fields');
function tpsc_validate_custom_fields() {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        // Check if field is required and empty
        if (isset($field['required']) && $field['required'] && empty($_POST[$field_key])) {
            wc_add_notice(
                sprintf(__('%s is a required field.', 'woocommerce'), $field['label']),
                'error'
            );
        }
        
        // Additional validation for specific field types
        if (!empty($_POST[$field_key])) {
            // VAT number validation example
            if ($key === 'vat_number') {
                if (!preg_match('/^[A-Z]{2}[0-9]+$/', $_POST[$field_key])) {
                    wc_add_notice(__('Please enter a valid VAT number.', 'woocommerce'), 'error');
                }
            }
            
            // Email validation for email type fields
            if ($field['type'] === 'email' && !is_email($_POST[$field_key])) {
                wc_add_notice(
                    sprintf(__('%s is not a valid email address.', 'woocommerce'), $field['label']),
                    'error'
                );
            }
        }
    }
}

// ============================================
// SAVE FIELD VALUES
// ============================================

add_action('woocommerce_checkout_create_order', 'tpsc_save_custom_fields', 10, 2);
function tpsc_save_custom_fields($order, $data) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        if (!empty($_POST[$field_key])) {
            $order->update_meta_data('_' . $field_key, sanitize_text_field($_POST[$field_key]));
        }
    }
}

// ============================================
// DISPLAY IN ORDER ADMIN
// ============================================

add_action('woocommerce_admin_order_data_after_billing_address', 'tpsc_display_admin_order_meta', 10, 1);
function tpsc_display_admin_order_meta($order) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    echo '<div class="tpsc-custom-fields-admin">';
    echo '<h3>' . __('Additional Information', 'woocommerce') . '</h3>';
    
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        $value = $order->get_meta('_' . $field_key);
        
        if ($value) {
            echo '<p><strong>' . $field['label'] . ':</strong> ';
            
            // Format display based on field type
            if ($field['type'] === 'checkbox') {
                echo $value ? __('Yes', 'woocommerce') : __('No', 'woocommerce');
            } elseif ($field['type'] === 'select' && isset($field['options'][$value])) {
                echo $field['options'][$value];
            } else {
                echo $value;
            }
            
            echo '</p>';
        }
    }
    
    echo '</div>';
}

// ============================================
// DISPLAY IN CUSTOMER EMAILS
// ============================================

add_filter('woocommerce_email_order_meta_fields', 'tpsc_email_order_meta_fields', 10, 3);
function tpsc_email_order_meta_fields($fields, $sent_to_admin, $order) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        $value = $order->get_meta('_' . $field_key);
        
        if ($value) {
            $display_value = $value;
            
            // Format display based on field type
            if ($field['type'] === 'checkbox') {
                $display_value = $value ? __('Yes', 'woocommerce') : __('No', 'woocommerce');
            } elseif ($field['type'] === 'select' && isset($field['options'][$value])) {
                $display_value = $field['options'][$value];
            }
            
            $fields[] = array(
                'label' => $field['label'],
                'value' => $display_value,
            );
        }
    }
    
    return $fields;
}

// ============================================
// DISPLAY IN ORDER DETAILS (MY ACCOUNT)
// ============================================

add_action('woocommerce_order_details_after_order_table', 'tpsc_display_order_meta_in_account');
function tpsc_display_order_meta_in_account($order) {
    $custom_fields = tpsc_get_custom_checkout_fields();
    $has_custom_fields = false;
    
    // Check if there are any custom fields with values
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        if ($order->get_meta('_' . $field_key)) {
            $has_custom_fields = true;
            break;
        }
    }
    
    if (!$has_custom_fields) {
        return;
    }
    
    echo '<h2>' . __('Additional Information', 'woocommerce') . '</h2>';
    echo '<table class="woocommerce-table woocommerce-table--custom-fields shop_table">';
    echo '<tbody>';
    
    foreach ($custom_fields as $key => $field) {
        $field_key = $field['section'] . '_' . $key;
        if ($field['section'] === 'order') {
            $field_key = $key;
        }
        
        $value = $order->get_meta('_' . $field_key);
        
        if ($value) {
            echo '<tr>';
            echo '<th>' . $field['label'] . '</th>';
            echo '<td>';
            
            if ($field['type'] === 'checkbox') {
                echo $value ? __('Yes', 'woocommerce') : __('No', 'woocommerce');
            } elseif ($field['type'] === 'select' && isset($field['options'][$value])) {
                echo $field['options'][$value];
            } else {
                echo nl2br($value);
            }
            
            echo '</td>';
            echo '</tr>';
        }
    }
    
    echo '</tbody>';
    echo '</table>';
}

// ============================================
// CONDITIONAL FIELD DISPLAY (JavaScript)
// ============================================

add_action('wp_footer', 'tpsc_checkout_conditional_fields_script');
function tpsc_checkout_conditional_fields_script() {
    if (!is_checkout()) {
        return;
    }
    ?>
    <script type="text/javascript">
    jQuery(document).ready(function($) {
        // Handle conditional fields
        $('#is_gift').change(function() {
            if ($(this).is(':checked')) {
                $('#gift_message_field').slideDown();
            } else {
                $('#gift_message_field').slideUp();
                $('#gift_message').val('');
            }
        }).change();
    });
    </script>
    <?php
}

// ============================================
// ADD CSS FOR BETTER STYLING
// ============================================

add_action('wp_head', 'tpsc_custom_checkout_styles');
function tpsc_custom_checkout_styles() {
    if (!is_checkout()) {
        return;
    }
    ?>
    <style>
        .tpsc-custom-fields-admin {
            margin-top: 20px;
            padding: 15px;
            background: #f8f9fa;
            border-left: 4px solid #007cba;
        }
        
        .tpsc-custom-fields-admin h3 {
            margin-top: 0;
            color: #007cba;
        }
        
        /* Optional: Add icons to custom fields */
        #vat_number_field label:before {
            content: "🏢 ";
        }
        
        #delivery_instructions_field label:before {
            content: "📝 ";
        }
        
        #referral_source_field label:before {
            content: "📣 ";
        }
        
        #is_gift_field label:before {
            content: "🎁 ";
        }
        
        #preferred_delivery_date_field label:before {
            content: "📅 ";
        }
    </style>
    <?php
}