Note on Expression Engine Add-on Mo' Variables and get:* in conditions

Mo Variables - get conditions.html

Testing how Mo Variables works with conditions

<code>id: {get:id}. {if "{get:id}" == ""}1{/if}{if "{get:id}" != ""}2{/if}{if get:id}3{if:else}4{/if}{if "{get:id}"}got id{/if}{if "{get:id}" == 0}0{/if}</code>

<pre>
{!--
url: /
result: id: . 4
url: /?id=
result: id: . 140
url: /?id=a
result: id: a. 23got id0

In other words:

"{get:id}" == "" 
closest approximation may be $_GET['id'] === "" (because $... == "" is like empty($...))

"{get:id}" == 0
is like isset($_GET['id'])

{if}{if:else}{/if}
is like !empty / empty

There is no actual equivalent to empty without using the advanced conditional if:else.

Ergo in most cases you want to use if:else.
--}
</pre>