title: link using $_GET whilst using isset cant find page
body: <p>Im currently trying to get a link:</p>
  
  <pre><code>  &lt;a href='?p=bid?Sale_ID=$Sale_ID'&gt;BID&lt;/a&gt;
  </code></pre>
  
  <p>to work but I keep getting a "Page you are requesting doesn´t exist" message, this page works if i use this link:</p>
  
  <pre><code>  &lt;a href='include/bid.php?Sale_ID=$Sale_ID'&gt;BID&lt;/a&gt;
  </code></pre>
  
  <p>this leads me to believe that my problem lies with the isset im using to include pages on link:</p>
  
  <pre><code>  &lt;?php
    if (isset($_GET['p']) &amp;&amp; $_GET['p'] != "") {
    $p = $_GET['p'];
    if (file_exists('include/'.$p.'.php')) {
    @include ('include/'.$p.'.php');
    } elseif (!file_exists('include/'.$p.'.php')) {
    echo 'Page you are requesting doesn´t exist&lt;br&gt;&lt;br&gt;';
    }
    } else {
    @include ('include/login-form.php');
    }
    ?&gt;
  </code></pre>
  
  <p>Ive tried adding another isset replacing p with q which just throws my pages in to dissaray.</p>
  
  <p>So my question is, is there a way around this?</p>
  
  <p>Thanks</p>