Question

An easy question about how php behaves:

getColor is a function of class Circle which returns either false or an object with the color as an attribute. If I do:

$res=$circle->getColor();
if ($res && $res->color=='white')
{
    echo "ok";
 } else {
    echo "no";
 }

I get “ok”, but if I do

if ($res=$circle->getColor() && $res->color=='white')
{
    echo "ok";
 } else {
    echo "no";
 }  

I get “no”. Why? I thought first condition is executed first. Isn’t it?

Answer 1

Because of operator precedence. Because && has higher precedence than = PHP is effective seeing this:

if ($res = ($circle->getColor() && $res->color=='white'))

In order to get the behavior you want, you should parenthesize the first condition:

if (($res = $circle->getColor()) && $res->color == 'white')