Question

When we have something like:

if (null === ($bar = $foo->getBar())) {

}

Are we doing three things on this single line ?
Are we:

1) Declaring a variable.

2) Attribute that variable a value.

3) Check if that variable value is null.

?

Answer 1

Yup, exactly like:

$bar = $foo->getBar();
if (null === $bar) {

}

$bar will receive the value returned by $foo->getBar(), and then the expression tests whether that (the result of the assignment expression, which is the value that got assigned to $bar) is === null. (And if this is the first use of $bar, then it’s creating a new variable.)