php的IF中的括号和赋值

Question

Question:

Code 1 and Code 2 has got 1 difference - brackets.

I do not get why 1st causes error but 2nd not.

Code 1:

if
(
    $response = $myObject->response($request)
    && $response2 = $myObject->response($response) // PHP Notice: Undefined variable: response 
)

Code 2:

if
(
    ($response = $myObject->response($request))
    && $response2 = $myObject->response($response) // Everything is OK
)

Answer 1

&& operator has higher precedence than = operator.

The brackets change the order of the evaluation to what you desire, as expressions in brackets are evaluated first(as they do in math).