code: public function getWeekBegin($intStartDay=0)
  	{
  		$intOffset = date('w', $this->strDate) - $intStartDay;
  
  		if ($intOffset < 0)
  		{
  			$intOffset += 7;
  		}
  
  		return strtotime('-' . $intOffset . ' days', $this->strDate);
  	}
docs: Return the begin of the week as timestamp
  
  @param integer $intStartDay The week start day
  
  @return integer The Unix timestamp