How do I call a PHP file and return the result?

[vigour]

I can't get this to work. I just want to check my database and return 1 or 0 depending on the result but nothing happens. What did I do wrong?

var username = $('#username').val();  
  
        //use ajax to run the check  
        $.post("check_username.php", { username: username },  
            function(result){  
                //if the result is 1  
                if(result == 1){  
                    //show that the username is available  
                    $('#username_availability_result').html(username + ' is Available');  
                }else{  
                    //show that the username is NOT available  
                    $('#username_availability_result').html(username + ' is not Available');  
                }  
        });

//connect to database  
mysql_connect('host', 'user', 'pass');  
mysql_select_db('database_name');  
  
//get the username  
$username = mysql_real_escape_string($_POST['username']);  
  
//mysql query to select field username if it's equal to the username that we check '  
$result = mysql_query('select username from users where username = "'. $username .'"');  
  
//if number of rows fields is bigger them 0 that means it's NOT available '  
if(mysql_num_rows($result)>0){  
    //and we send 0 to the ajax request  
    echo 0;  
}else{  
    //else if it's not bigger then 0, then it's available '  
    //and we send 1 to the ajax request  
    echo 1;  
} 

[Bonesnap]

If you're using Firefox I would install the Firebug add-on and check the console; it will report AJAX and JavaScript errors. Chrome has similar functionality.

Everything at first glance seems to be okay. Things I would check if I were in your situation:

- Check the path of the PHP script and make it's correct in relation to the JavaScript file. If "nothing happens" it's usually because there's a path issue of some kind.
- Check the variables along the way and either echo/alert/log/etc as you go to see if values are actually being reported as you expect.

Also, people here are going to yell at you for using the MySQL extension instead of the MySQLi or PDO extension. This is me not yelling at you. But really. Stop using it.