Find a record using the value of a cookie

I can not find a value in the database by a select by reference to a variable coming from a cookie :

$query = "SELECT * FROM carrinho WHERE dono = '$dono'";

However, if you search using the variable text,

$query = "SELECT * FROM carrinho WHERE dono = 'd2466de8-ccde-4939-f756-bf427f'";

The desired values are found.

The $dono fault variable comes from a cookie : $dono = $_COOKIE["id_user"];

And if you give% of the variable the same text appears echo