PHP - Declare variable in if statement and use it in the same statement

I want to declare a variable in a if statement and use it in the same statement. Is this simply not possible?

Example of problem (not actual use case though...):

if ($test = array('test'=>5) && $test['test'] === 5) {
    echo 'test';
} else {
    echo 'nope';
}

Error message:

NOTICE Undefined variable: test on line number 6