title: cURL aspx posting issue
body: <p>I have been developing php curl script for <strong>www.pool.com</strong></p>
  
  <p>I could handle viewstate and event problems but I see other issues about posting.</p>
  
  <pre><code>Invalid postback or callback argument.  Event validation is enabled using 
  &lt;pages enableEventValidation="true"/&gt; in configuration or &lt;%@ Page
  EnableEventValidation="true" %&gt; in a page.  For security purposes, this feature verifies
  that arguments to postback or callback events originate from the server control that 
  originally rendered them.  If the data is valid and expected, use the 
  ClientScriptManager.RegisterForEventValidation method in order to register the postback or
  callback data for validation.
  </code></pre>
  
  <p>In first part , I'm getting eventtarget ,viewstate and eventvalidation and it's fine.Then I'm clicking <em>advanced search</em> through posting eventtarget(you can see in code). It is also fine. However, I'm posting other data which is called CtlBucket_Search1:txtKeyWordCharacters it gives me error invalid postback ..</p>
  
  <p>I don't understand why it has error.</p>
  
  <p>Codes :</p>
  
  <pre><code>&lt;?php
  
  $url = "http://www.pool.com/viewlist.aspx";
  $ckfile = tempnam("/tmp", "CURLCOOKIE");
  $useragent = 'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/533.2 (KHTML, like Gecko) Chrome/5.0.342.3 Safari/533.2';
  
  $f = fopen('log.txt', 'w'); // file to write request header for debug purpose
  
  /**
  Get __VIEWSTATE &amp; __EVENTVALIDATION
   */
  $event = 'CtlBucket_Search1$lbtSearchToggleAdv';
  $ch = curl_init($url);
  curl_setopt($ch, CURLOPT_COOKIEJAR, $ckfile);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
  
  $html = curl_exec($ch);
  
  curl_close($ch);
  
  preg_match('~&lt;input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="(.*?)" /&gt;~', $html, $viewstate);
  preg_match('~&lt;input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="(.*?)" /&gt;~', $html, $eventValidation);
  
  $viewstate = $viewstate[1];
  $eventValidation = $eventValidation[1];
  
  
  
  /**
   * Start Posting process
   */
  $ch = curl_init();
  
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, false);
  curl_setopt($ch, CURLOPT_COOKIEJAR, $ckfile);
  curl_setopt($ch, CURLOPT_COOKIEFILE, $ckfile);
  curl_setopt($ch, CURLOPT_HEADER, FALSE);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
  curl_setopt($ch, CURLOPT_REFERER, $url);
  curl_setopt($ch, CURLOPT_VERBOSE, 1);
  curl_setopt($ch, CURLOPT_STDERR, $f);
  curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
  
  // Collecting all POST fields
  $postfields = array();
  $postfields['__EVENTTARGET'] = $event;
  $postfields['__EVENTARGUMENT'] = "";
  $postfields['__VIEWSTATE'] = $viewstate;
  $postfields['__EVENTVALIDATION'] = $eventValidation;
  // Problem is below
  $postfields['CtlBucket_Search1:txtKeyWordCharacters'] = 4;
  
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
  $ret = curl_exec($ch); // Get result after login page.
  </code></pre>