title: Simple redirect in Symfony2 by changing a query string parameter, NOT route related
body: <p>This should be simple, and I've been searching all over Google, but I keep coming up with 'route' related advice.</p>
  
  <p>I just want to perform a redirect to the same page and modify one of the query string parameters (either to clear one or set one).</p>
  
  <p>I can't see how to do this anywhere.</p>
  
  <p>An option could be to completely generate the URL manually and use this I guess, but that doesn't seem a very good method:</p>
  
  <pre><code>$this-&gt;router-&gt;generate("http://domain.com?a=1")
  </code></pre>