help me plzz ! [php hard question]

Question

hi,

i know if we a varible like $var =5;

and i will make :

$var2 = $var--;

the result of $var2 will be 5;
and result of $var will convert to 4;
and if we make :
$var3 = --$var2;
the var3 will be 4 and var2 will convert to 4.

Why :

$num = 5;
echo $num * $num--;
the result of $num is 20 ????????????!

img to the oringnal question :

https://imgur.com/a/VF3OB4g

Answer 1

ok thanks :)