no?
I don't see your example as a proof for that.
$x is incremented and the return value of the post increment (1) is passed as the argument 3
$x is incremented and the return value of the pre increment (3) is passed as argument 4.
$x is now 3.
argument 1 is an alias for $x. 3
argument 2 is an alias for $x. 3
argument 3 is 1.
argument 4 is 3.