/**
 * Calculates a hash string based on additional parameters in the url. This is used to cache pages with more parameters than just id and type
 *
 * @return	void
 * @see reqCHash()
 */
function makeCacheHash()	{
	$GET = t3lib_div::_GET();
	
	/**
	 * 
	 */
	$myExtParams = t3lib_div::GPvar('tx_myext_pi1');				
	if(sizeof($myExtParams) >= 1) {
		$myExtQstring = '&id='.$this->id;
		$GET = array('id' => $this->id);
		$GET['tx_myext_pi1'] = array();
		foreach ($myExtParams as $varName => $varValue) {
			$GET['tx_myext_pi1'][$varName] = $varValue;
			$myExtQstring .= '&tx_myext_pi1['.$varName.']='.$varValue;
		}
		
		$cHash_array = t3lib_div::cHashParams($myExtQstring);
		$this->cHash = t3lib_div::shortMD5(serialize($cHash_array));			
	}
	/**/
		
	if ($this->cHash && is_array($GET))	{
		$this->cHash_array = t3lib_div::cHashParams(t3lib_div::implodeArrayForUrl('',$GET));
		$cHash_calc = t3lib_div::shortMD5(serialize($this->cHash_array));

		if ($cHash_calc!=$this->cHash)	{
			if ($this->TYPO3_CONF_VARS['FE']['pageNotFoundOnCHashError']) {
				$this->pageNotFoundAndExit('Request parameters could not be validated (&cHash comparison failed)');
			} else {
				$this->set_no_cache();
				$GLOBALS['TT']->setTSlogMessage('The incoming cHash "'.$this->cHash.'" and calculated cHash "'.$cHash_calc.'" did not match, so caching was disabled. The fieldlist used was "'.implode(',',array_keys($this->cHash_array)).'"',2);
			}
		}
	}
}