How To – Display custom question to product page with validation

add_action('woocommerce_after_add_to_cart_button', 'tuskcode_custom_question_product', 10 );

add_action('woocommerce_add_to_cart_validation', 'tuskcode_add_to_cart_validate', 20, 5 );


function tuskcode_custom_question_product(){
	
	global $product;
	$product_id = $product->get_id();
	
	//see if raffle product or not.
	$is_raffle_product = get_post_meta( $product_id, '_rpwoo_ckb', true );  //yes - no or empty
	
	if( $is_raffle_product !== 'yes') return;
	
	//if( $product_id != 77 ) return;
	
	echo "<p> What's the capital city of England? ";
	
		echo "<select name='question_raffle_product' style='font-size: 1rem; color: red;' class='custom-question'>
				<option value='' selected > 	Select </option>
				<option value='paris' > 		Paris </option>
				<option value='madrid' > 		Madrid </option>
				<option value='london' > 		London </option>
			</select>";
	
	echo "</p>";
}

function tuskcode_add_to_cart_validate( $validate, $product_id, $quantity, $variation_id = 0, $variation = null ){
	
	if( isset( $_POST['question_raffle_product'] ) ){
		
		$value = trim( sanitize_text_field( wp_unslash( $_POST['question_raffle_product'])) );
		
		//no answer selected, force to select one
		if( $validate && $value == '' ){
			$validate = false;
			wc_add_notice( 'Hey, select an answer to the question, please. Thank you.', 'error' );
		}
		
		//answer selected, but wrong one is picked.
		if( $validate && $value !== 'london' ){
			$validate = false;
			wc_add_notice( 'Hey, work on your general knowledge', 'error' );
		}
		
	}else{
		//nothing to do, this product does not have a question to answer
	}
	
	return $validate;
	
}