I would store the product data on the server and only pass the product id so you don't have to trust the user. It does make it more complicated though.
But you did not state it in this topic and thus you were setting up some respondents for one of your many grillings telling them how wrong they are, sighing
When you are stating things are not being output/echoed, you need to be specific about what output you did and didn't get, since we are not standing right
Also, for some reason I never see the text that is echoed.
I've tested it in PHPMyAdmin using
SELECT `fullname` FROM `client` WHERE `fullname` = 'test';
It worked correctly.