php - ajax checking username onblur -

here case guys, i'm trying check username on onblur event of ajax , checking username availability in mysql database.

here ajax script =>

document.getelementbyid("r_username").onblur = function(){         var http = false;         var error = document.getelementbyid("error_username");         var numletter = /^[a-za-z-0-9]+$/;         if (this.value==""){             error.innerhtml = "empty field !!!";             error.style.display = "inline";         } else {             if (this.value.match(numletter)){                 if (window.xmlhttprequest){                     http = new xmlhttprequest();                 } else {                     http = new activexobject("microsoft.xmlhttp");                 }                 if (http){                     http.open("post","./config/ajaxusernameemail.php",true);                     http.setrequestheader("content-type", "application/x-www-form-urlencoded");                     http.onreadystatechange = function(){                         if (http.readystate==4 && http.status==200){                          }                     };                     http.send("r_username=" + document.getelementbyid("r_username").value);                 }                 error.innerhtml = "";                 error.style.display = "none";             } else {                 error.innerhtml = "invalid number !!!";                 error.style.display = "inline";             }         }     }; 

ajax working , .php file script below =>

class checking{ private $con,$query,$flag; public function __construct($con,$query){     $this->con   = $con;     $this->query = $query; } public function func(){     if (mysqli_connect_errno()==0){         if ($result = mysqli_query($this->con,$this->query)){             if ($data = mysqli_fetch_assoc($result)){                 return $this->flag = true;             } else {                 return $this->flag = false;             }         }     } } }  if (isset($_post['r_username'])){     $check = new checking($connection,"select username users username='" . $_post['r_username'] . "'");  } else {     header("location: http://" . $mysql->host . "/index.php"); } 

everything working fine , here problem , want connect somehow files , mean want know in .js file when username matching in database , when not , because want more action in .js file , can not set "flag" (variable me that). ideas ? :)))

in more details , .js file in registration.php file , , how can see guys .js file invoking ajax ajaxusernameemail.php file, want somehow know when username matching , when not , because want in registration.php file more actions (notifications) during matching

the code bit more so:

$return = 'fail';  class checking {      public function __construct($con, $query)     {         $this->con = $con;         $this->query = $query;         self::func()     }      public function func()     {         $result = 'ok';         if (mysqli_connect_errno()==0){             if ($result = mysqli_query($this->con,$this->query)){                 $result = mysqli_num_rows($result) > 0? 'user_exists' : 'user_doesnt_exist';             }         }         return $result;     }  }  if( $_post['r_username'] ){     $desired = mysqli_real_escape_string($_post['r_username']);     $return = new checking($connection,"select username users username='$desired'"); } echo $return; 

also, should worried escaping user input, , may want jquery ajax stuff.

the checking on client side, should go this:

if (http.readystate==4 && http.status==200){     switch (http.responsetext){         case 'fail':             //the username not provided         break;         case 'user_exists':             //the username exists         break;         case 'user_doesnt_exist':             //the username not found on database, continue         break;      } }