// global xmlhttprequest object
	var xmlHttp = false;
	

	
	/** AJAX functions **/
	
	// constants
	var REQUEST_GET		= 0;
	var REQEST_POST		= 2;
	var REQUEST_HEAD	= 1;
	var REQUEST_XML		= 3;
	
	
	
	/**
	 * instantiates a new xmlhttprequest object
	 *
	 * @return xmlhttprequest object or false
	 */
	function getXMLRequester( )
	{
		var xmlHttp = false;
				
		// try to create a new instance of the xmlhttprequest object		
		try
		{
			// Internet Explorer
			if( window.ActiveXObject )
			{
				for( var i = 5; i; i-- )
				{
					try
					{
						// loading of a newer version of msxml dll (msxml3 - msxml5) failed
						// use fallback solution
						// old style msxml version independent, deprecated
						if( i == 2 )
						{
							xmlHttp = new ActiveXObject( "Microsoft.XMLHTTP" );	
						}
						// try to use the latest msxml dll
						else
						{
							
							xmlHttp = new ActiveXObject( "Msxml2.XMLHTTP." + i + ".0" );
						}
						break;
					}
					catch( excNotLoadable )
					{						
						xmlHttp = false;
					}
				}
			}
			// Mozilla, Opera und Safari
			else if( window.XMLHttpRequest )
			{
				xmlHttp = new XMLHttpRequest();
			}
		}
		// loading of xmlhttp object failed
		catch( excNotLoadable )
		{
			xmlHttp = false;
		}
		return xmlHttp ;
	}
	
	
	/**
	 * sends a http request to server
	 *
	 * @param strSource, String, datasource on server, e.g. data.php
	 *
	 * @param strData, String, data to send to server, optionally
	 *
	 * @param intType, Integer,request type, possible values: REQUEST_GET, REQUEST_POST, REQUEST_XML, REQUEST_HEAD default REQUEST_GET
	 *
	 * @param strData, Integer, ID of this request, will be given to registered event handler onreadystatechange', optionally
	 *
	 * @return String, request data or data source
	 */
	function sendRequest( strSource, strData, intType, intID )
	{
	    if( !strData )
			strData = '';
	    // default type (0 = GET, 1 = xml, 2 = POST )
		if( isNaN( intType ) )
			intType = 0; // GET
	
		// previous request not finished yet, abort it before sending a new request
		if( xmlHttp && xmlHttp.readyState )
		{
			xmlHttp.abort( );
			xmlHttp = false;
		}
			
		// create a new instance of xmlhttprequest object
		// if it fails, return
		if( !xmlHttp )
		{
			xmlHttp = getXMLRequester( );
			if( !xmlHttp )
				return;
		}
		// parse query string
		if( intType != 1 && ( strData && strData.substr( 0, 1 ) == '&' || strData.substr( 0, 1 ) == '?' ) ){
			strData = strData.substring( 1, strData.length );
		}

		// data to send using POST
		var dataReturn = strData ? strData : strSource;
		
		switch( intType )
		{
		    case 1:	// xml
				strData = "xml=" + strData;
			case 2: // POST
				// open the connection 
				xmlHttp.open( "POST", strSource, true );
				xmlHttp.setRequestHeader( 'Content-Type', 'application/x-www-form-urlencoded' );
				xmlHttp.setRequestHeader( 'Content-length', strData.length );
				break;
			case 3: // HEAD
				// open the connection 
				xmlHttp.open( "HEAD", strSource, true );
				strData = null;
				break;
			default: // GET
			    // open the connection 
				var strDataFile = strSource + (strData ? '?' + strData : '' );
				//in nächster zeile fliegt SP1? rauß
				//alert("switch GET --> strDataFile "+strDataFile);
				//alert(xmlHttp);
				xmlHttp.open( "GET", strDataFile, true );
				//alert("xmlHttp.open --> OK");
				strData = null;
		}
		
		// set onload data event-handler
		xmlHttp.onreadystatechange = new Function( "", "processResponse(" + intID + ")" ); ;

		// send request to server
		xmlHttp.send( strData );	// param = POST data
		
		return dataReturn;
	}
		
	
	/**
	 * process the response data from server
	 *
	 * @param intID, Integer, ID of this response
	 */
	function processResponse( intID )
	{
		// status 0 UNINITIALIZED open() has not been called yet.
		// status 1 LOADING send() has not been called yet.
		// status 2 LOADED send() has been called, headers and status are available.
		// status 3 INTERACTIVE Downloading, responseText holds the partial data.
		// status 4 COMPLETED Finished with all operations.
		switch( xmlHttp.readyState )
		{
			// uninitialized
			case 0:
			// loading
			case 1:
			// loaded
			case 2:
			// interactive
			case 3:
				break;
			// complete
			case 4:	
				// check http status
				if( xmlHttp.status == 200 )	// success
				{
					processData( xmlHttp, intID );
				}
				// loading not successfull, e.g. page not available
				//else
				//{
				//	if( window.handleAJAXError ){
				//		handleAJAXError( xmlHttp, intID );
				//	}
				//	else{
				//		alert( "ERROR\n HTTP status = " + xmlHttp.status + "\n" + xmlHttp.statusText ) ;
				//	}
				//}
		}
	}
	
	/** End AJAX functions **/