How to write does not exist in PHP
<p>So I have an if statement in PHP that looks like this:</p>

<pre><code>if ($_GET['Squares'] != 0)
</code></pre>

<p>but really I need to check if the variable squares has been passed via the url. So it needs to be if squares doesn't exist. I tried the following but it throws errors.  </p>

<pre><code>if (!isset $_GET['Squares'])
</code></pre>

<p>Can anyone tell me what the correct syntax is please?</p>
