Q: using a function call directly in the 'IF' condition . Using PHP5.3, I can use a function directly in a condition,like this  :
if(my_function($var) == 'hello') {...}

But sometimes, even if I know what the function would return, I have a PHP bug and I have to do like this :
$result = another_function($var);
if($result == 'world') {...}

If both functions would return a string, why can I use the first and not the second ? I want to understand what the if condition can accept. Are all PHP natives functions are ok ? does the if condition doesn't want a method MyObject->my_function($var) ?
