-> is an operator indicating that the expression on the right is a member of the object on the left. It is not a comparison operator.
=> is an operator used in certain cases (such as defining an array via the array() function) to indicate that the expression on the left is an array key associated with an array value on the right -- again, not a comparison operator.
= is the "greater than or equal to" comparison operator (the inverse being <= ).
== is the "equal to" comparison operator, which is probably what you want to use where you are currently using the => operator.