How to add a custom field to checkout tab in woocommerce?

@lew 

To add a custom field to the checkout tab in WooCommerce, you can follow these steps:

1. Create a custom field: You can add a custom field to the checkout page by using the "woocommerce_checkout_fields" filter. You can add this filter in your theme's functions.php file or in a custom plugin. Here's an example of how to add a custom field called "Custom Field" to the checkout page:

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function custom_add_checkout_field( $fields ) {
    $fields['order']['custom_field'] = array(
        'type' => 'text',
        'label' => 'Custom Field',
        'placeholder' => 'Please enter your custom field',
        'required' => true,
    );
    return $fields;
}
add_filter( 'woocommerce_checkout_fields', 'custom_add_checkout_field' );

1. Modify the checkout form template: Once you have added the custom field to the checkout fields using the filter, you need to modify the checkout form template to display the custom field. You can do this by copying the "form-checkout.php" template file from the WooCommerce plugin directory to your theme directory under "woocommerce/templates/checkout/". Then, you can add the following code where you want the custom field to appear in the checkout form:

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<?php
woocommerce_form_field( 'custom_field', $checkout->checkout_fields['order']['custom_field'], $checkout->get_value( 'custom_field' ) );
?>

1. Validate and save the custom field data: You can also add validation and save the custom field data to the order meta using the "woocommerce_checkout_posted_data" hook. Here's an example of how to validate and save the custom field data:

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function custom_process_checkout_field() {
    if ( ! $_POST['custom_field'] ) {
        wc_add_notice( 'Please enter a value for the custom field.', 'error' );
    }
}
add_action( 'woocommerce_checkout_process', 'custom_process_checkout_field' );

function custom_update_order_meta( $order_id ) {
    if ( ! empty( $_POST['custom_field'] ) ) {
        update_post_meta( $order_id, 'Custom Field', sanitize_text_field( $_POST['custom_field'] ) );
    }
}
add_action( 'woocommerce_checkout_update_order_meta', 'custom_update_order_meta' );

These steps will allow you to add a custom field to the checkout tab in WooCommerce and save the data to the order meta.