Add Sample Custom Product Field for Testing

Sample Custom Field

class Product_Custom_Field {
	public function __construct() {
		add_action( 'woocommerce_before_add_to_cart_button', array( $this, 'display_custom_field' ) );
		add_filter( 'woocommerce_add_cart_item_data', array( $this, 'add_cart_item_data' ), 10, 2 );
		add_filter( 'woocommerce_get_item_data', array( $this, 'get_item_data' ), 10, 2 );
		add_action( 'woocommerce_checkout_create_order_line_item', array( $this, 'checkout_create_order_line_item' ), 10, 4 );
	}

	public function display_custom_field() {
		echo '<div class="custom-field-wrapper">';
		echo '<label for="custom_field">Custom Field:</label>';
		echo '<input type="text" id="custom_field" name="custom_field" />';
		echo '</div>';
	}

	public function add_cart_item_data( $cart_item_data, $product_id ) {
		if ( isset( $_POST['custom_field'] ) ) {
			$cart_item_data['custom_field'] = sanitize_text_field( $_POST['custom_field'] );
		}
		return $cart_item_data;
	}

	public function get_item_data( $item_data, $cart_item_data ) {
		if ( isset( $cart_item_data['custom_field'] ) ) {
			$item_data[] = array(
				'key'     => 'Custom Field',
				'value'   => $cart_item_data['custom_field'],
				'display' => '',
			);
		}
		return $item_data;
	}

	public function checkout_create_order_line_item( $item, $cart_item_key, $values, $order ) {
		if ( isset( $values['custom_field'] ) ) {
			$item->add_meta_data( 'Custom Field', $values['custom_field'], true );
		}
	}
}

new Product_Custom_Field();