No comprendo que el resultado sea 2

Question

$a=2; $b=a++
https://code.sololearn.com/WkZFWDAHHr8Y/?ref=app

Answer 1

Here first the value of a is assigned to b and then the value of a is incremented

So final values are
a=3 b=2

Answer 2

a=2;
b=a++;
es egual
b=a
a=a+1