why didn't he just add a else section on the original if(!empty($_GET['id']) instead of messing with an isset, and

Seth Warner, there are tons of ways to solve the same problem. It is common to see developers check for both

if (!empty($var) && isset($var) ) { // Do code }

One big reason to use isset() AND !empty is because !empty will not throw you a notice in your php error log. These notices can be useful when debugging so isset() is good for that.

Yeah that is one way to go about it. The isset will basically accomplish the same thing but if you throw in the else statement your suggesting, then you will have control of what the error message will output rather than the standard error message isset will generate

Although - I would write this the other way around because conditionals get checked left -> right :)

<?php

isset($var) && !empty($var)

otherwise you'll get an error thrown on the first empty check because the $var you're checking isn't set.

Generally speaking, you probably own't need to use the empty function. If it's empty (hasn't been defined a type) or has a type, but that type is empty (like an empty array) it will return a boolean false - so you can shorten to:

<?php

isset($var) && $var

// i.e. it is set, and there's something sitting inside it with a value.

Come to think of it, I haven't found a need to use 'empty' since I started!