Set up parameter not recognized from parse request
<p>This has been playing on my mind for a while, I need to check that the user has entered the correct parameters, how do I do check this in an if statement in php? 
Users enters as follows;</p>

<pre><code>www.domain.com/?amnt=100&amp;from=AAA&amp;to=BBB
</code></pre>

<p>so I need to check if they enter something as follows;</p>

<pre><code>www.domain.com/?xxx=100&amp;yyy=AAA&amp;to=BBB
</code></pre>

<p>///////
Code is now as follows;</p>

<pre><code>    //1000 Required parameter is missing
if ($amnt == null || $from==null || $to==null) {
    $error_code = 1000;
    $returnXML = new XML();
    $returnXML-&gt;CreateError($error_code,$error_msg[$error_code]);
    echo '&lt;META HTTP-EQUIV="Refresh" Content="0; URL=error.xml"&gt;';
    exit;
}
//1100 Parameter not recognized
if(!isset($_GET['amnt'], $_GET['from'], $_GET['to']))
{
    $error_code = 1100;
    $returnXML = new XML();
    $returnXML-&gt;CreateError($error_code,$error_msg[$error_code]);
    echo '&lt;META HTTP-EQUIV="Refresh" Content="0; URL=error.xml"&gt;';
    exit;
}
</code></pre>

<p>it returns the first IF when I request ../?xxx=100&amp;yyy=GBP&amp;to=USD, it makes logical sense, but how do I get it to return the second IF, if the parameters are not entered?</p>
