CI框架中使用ajax操作数据库问题

<script>//调用方法用ajax操作add_dbdata.phpvar xmlHttpfunction add_dbdata(str,str1){			//alert(str);	if (str=="")	{	document.getElementById("txtHint").innerHTML="";	return;	}	if (window.XMLHttpRequest)	{// code for IE7+, Firefox, Chrome, Opera, Safari	xmlhttp=new XMLHttpRequest();	}	else	{// code for IE6, IE5	xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");	}	xmlhttp.onreadystatechange=function()	{	if (xmlhttp.readyState==4 && xmlhttp.status==200)	{	document.getElementById("txtHint").innerHTML=xmlhttp.responseText;	}	}	//xmlhttp.open("GET","add_dbdata.php?q="+str,true);	//alert(str1);	//alert(str);		xmlhttp.open("GET","add_dbdata.php?q="+str,true);	   //xmlhttp.open("GET","<?=base_url()?>project_c/add_zijiedian/"+str1+str,true);  这样写，也不好使，不知道哪有问题 	xmlhttp.send();}

<?phpheader("Content-type:text/html;charset=utf8");$q=$_GET["q"];$q=(int)$q;echo "<script>alter('kkkkkkk');</script> ";$con = mysql_connect('localhost', 'root', '');if (!$con) { die('Could not connect: ' . mysql_error()); }mysql_select_db("test", $con);mysql_query("set names utf8");//$sql = " SELECT * FROM ecm_acategory ";$sql = " insert into data (name) values('999')";echo $sql;$result = mysql_query($sql);mysql_close($con);?>

	//插入预算表					$this->db->query("select @myLeft:=PLeft from constrproj where  ConstrProjName = '$dangqiandianname' ");										$this->db->query("UPDATE constrproj SET PRight = PRight + 2 WHERE PRight > @myLeft");										$this->db->query("UPDATE constrproj SET PLeft = PLeft + 2 WHERE PLeft > @myLeft");								$query3 = $this->db->query("select * from constrproj where ConstrProjID= ( SELECT min(ConstrProjID) from constrproj)");						$arr = $query3->result_array();					$ParentID = $arr[0]['ConstrProjID'];										//echo '<script>alert("'.$ParentID.'");</script>';							$this->db->query("INSERT INTO constrproj(ConstrProjName,PLeft,PRight,ParentID,KindLvl) VALUES('$zijiediandianname',@myLeft + 1, @myLeft +2,'$ParentID',1)" );										$query2 = $this->db->query("select * from constrproj");				    $result_count2 = count($query2->result());