title: How to test for dynamic URL parameters being defined in PHP?
body: <p>I'm calling a <code>fpdf</code> file through an URL. For some calls I need to supply specific parameters, which are only used on specific calls. I cannot update all calls to the FPDF file, so I want to test inside the file, whether a URL parameter exists.</p>
  
  <p>I'm trying like this:</p>
  
  <pre><code>&lt;?php
   require('fpdf.php');
   ini_set('display_errors', 1);
   error_reporting(E_ALL);
   import_request_variables("GP", "rvar_");
  
   if (isset($rvar_store){
   ... set something
   }
  </code></pre>
  
  <p>So the URL parameter <code>store</code> will be passed on some php-calls, while there is no parameter on others. </p>
  
  <p>The above doesn't work (I get a blank page).</p>
  
  <p><strong>Question</strong>:<br>
  How do I test for a URL parameter? I need to test if it is defined?</p>
  
  <p><strong>EDIT:</strong><br>
  My url called will look like this:</p>
  
  <pre><code> fpdf/item.php?iln="+ilns+"&amp;sprache="+locale+"&amp;bestellkeys="+bestellkeys;
  </code></pre>
  
  <p>or when I have my spec param:</p>
  
  <pre><code>  fpdf/bestellung.php?iln="+ilns+"&amp;sprache="+locale+"&amp;bestellkeys="+bestellkeys+"&amp;store=true";
  </code></pre>