在文本框的onBlur事件上执行JavaScript函数

Question

I wrote following :

function loginName(txtLogin){
    var l = document.getElementById('txtLogin').value;
    <?php
        $query = sprintf("Select * from register where LoginName='%s'",
                        mysql_real_escape_string(l));

        //$query =  "Select * from register where UserName=$Username and     Pwd=$Password";
        $result = mysql_query($query);
        if($result)
        {
            $num_rows =  mysql_num_rows($result);
        }
    ?>
    if($num_rows < 1)
    {
        return true;
    }
    else
    {
        return false;
    }
}

and call that function on onBlur event as below:

 $('#txtLogin').blur(function() {
      if(loginName('txtLogin'))
      {
          //alert('Email is valid');
      }
      else
      {
          alert('Type another login name.');
      }
   });

But its not showing error when I enter same login name as exist in database.please help.

Answer 1

you can not execute PHP inside <script> tags because it's only executing in client side, and PHP is a server side language. Instead of this, you need to use AJAX to check the validity of the username. BTW, you directly copy&paste'd your code from somewhere because return is not a valid keyword outside of a method. if you are familiar with jQuery (a javascript library), I recommend using it for the AJAX part.

Answer 2

PHP code is run at the time page gets parsed. If you're expecting it to run when the JS function is executed then you will need to write your PHP code in an external file and call that by AJAX.

Answer 3

PHP runs on the server and outputs some text.

That text is then interpreted as HTML and JavaScript by the browser.

When you call a JavaScript functions, then any PHP inside it will already have run. You can't pass a variable from JavaScript to PHP like that.

You must make a new HTTP request (eg by submitting a form, or using Ajax).