In php, what does it mean to enclose a function call inside parenthesis?

In the framework I'm working in, Phpfox, I see this function invocation signature throughout:

(($sPlugin0 = Phpfox_Plugin::get('user.service_user_isuser')) ? eval($sPlugin1) : false);

I see no apparent purpose of the outer parenthesis since:

1. $sPlugin1 is read from enclosing scope and
2. $sPlugin0 is passed to enclosing scope after being assigned.

What is the purpose of the outer parens? What I'm getting at is is there some functional aspect to the outer parens like in Javascript?

Updated: I know that outer parens would be meaningless in an expression such as

(1 + 1)

that's not what I'm asking.

I now conclude as I suspected that in php these outer parens do nothing.

Thanks