username check with db without submit

[J_Sivaani]

hai friends ,
i have to check the entered username in the textbox is present in the database or not without submitting the form.i am searching in ajax but i couldn't get clear script. please send me any script if you have.

Thanks in advance
have a nice day.🙂
Take care,
j.sivaani

[jib0]

Hi,

Firstly, you'll need a JavaScript code like this:

<script type="text/javascript">
  var http = createRequestObject();

  function createRequestObject() {
    var req;

if (window.XMLHttpRequest) {
  req = new XMLHttpRequest();
  if (req.overrideMimeType)
    req.overrideMimeType("text/xml");
} else if (window.ActiveXObject) {
  try {
    req = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (e) {
    try {
      req = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (e) {}
  }
}

if (req == null)
  alert("Problem creating the XMLHttpRequest object.");

return req;
  }

  function checkUser(user) {
    if (http != null) {
      http.open("POST", "check.php", false);
      http.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      http.send("user=" + user);

  if (http.readyState == 4 && http.status == 200)
    return http.responseText;
}

return "Error";
  }
</script>

it will make a request to the user.php script:

if (isset($_POST['user'])) {
  $sql = sprintf("SELECT * FROM Users WHERE username = '%s';", mysql_real_escape_string($_POST['user']));
  $res = mysql_query($sql);

  if ($res) {
    if (mysql_num_rows($res) > 0)
      echo 'already exists';
    else
      echo "does't exists";
  } else
    echo 'Database error';
}

Now you should call the script for example with this simple HTML:

<input type="text" name="user" size="20" maxlength="20" />
<a href="#" onclick="javascript:checkUser(this.user.value)">check</a>