Notice: Undefined index: userid in /home/milkman/application/releases/71e6403c65f847c6c0cd58733cd22f2a2c31f3c7/public/cart/addremovecart/index.php on line 30

Notice: Undefined index: userid in /home/milkman/application/releases/71e6403c65f847c6c0cd58733cd22f2a2c31f3c7/public/cart/addremovecart/index.php on line 38
mySQL Error on Query:
SELECT * FROM carts WHERE userid =