在phpMyAdmin中触发触发器时显示消息

I have a table where stock quantity is recorded. I set trigger to warn the user when stock goes low. When testing it, the trigger fires, displays the message, but the stock is not updated. What do I do wrong? Is there another way to set the trigger (not using SIGNAL SQLSTATE)? I use phpMyAdmin 4.2.7.1 in uWamp. Thank you for suggestions.I have a table where stock quantity is recorded