I have recently decided to take the plunge and try my hand at php, Ia m enjoying it and I have so far created a login/logout and register page.

But I am having trouble with the forgot password script. Please can you help and be kind as it is my first time posting.
This is the error that i am getting Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in
PHP Code:
<?php

if (isset($_POST['submit']))
{    
    
    
mysql_connect("host"username", "password") or die("could not connect to the database");
    mysql_select_db("
db_name") or die("could not select database");

    
    
$username = $_POST['username'];
    
$email = $_POST['email'];

    
    
$sql = mysql_query("SELECT FROM `usersWHERE `username` = '$username' AND `email` = '$email'");
    
$result = mysql_num_rows($sql);

    
    if (!
$result)
    {
        die (mysql_error());
    }

    
    if (
$result == 1)
    {
        
$rows = mysql_fetch_array($result);
        
$password = $rows['password'];
        
$email = $rows['email'];
        
$subject ="Password request";
        
$header = "fromomarmuzaffar@live.co.uk";
        
$body = "Your password is " . $password

        mail (
$email$subject$header$body); 
        print("
an email containning the password has been sent to you");
    }else
    {
        echo ("
No such user exists in the systemPlease try again");
    }

}

?>

<html>
<head>
    <title>
        forgot password form
    </title>
</head>
    <body>
        <form action = "
<?php $_SERVER['PHP_SELF'];?>" method = "POST">
            <p>
                <label for = "username">Username:</label>
                <input type = "text" name = "username" />
            </p>
            <p>
                <label for = "email">Email:</label>
                <input type = "text" name = "email" />
            </p>
            <p>
                <input type = "submit" name="submit" />
                <input type = "reset" name = "reset" />
            </p>
        </form
    </body>
</html>