I am working on a user account system and I am needing to update records in a SQL database. I have tried looking it up but all the solutions I have found don't seem to work. My table looks something like this

```
   userId userName userCoins
     30      Bob       0

```

And I am wanting to update the userName so it looks like this

```
userId userName userCoins
 30      jim       0

```

-

```
<?php
    ob_start();
    session_start();
    include_once 'dbconnect.php';

    $res=mysql_query("SELECT * FROM users WHERE userId=".$_SESSION['user']);
    $userRow=mysql_fetch_array($res);
    if ( isset($_POST['btn-signup']) ) {
        //This is where I am trying to update

        UPDATE users SET userName = 'jim' WHERE userCoins=0;
    }
?>
<!DOCTYPE html>
<html>
    <?php header("Access-Control-Allow-Origin: http://www.py69.esy.es"); ?>
    <head></head>
    <body>
        <center>
        <h3>Welcome, <?php echo $userRow['userName']; ?>. You Currently Have <span id="services"><?php echo $userRow['userCoins']; ?></span> Service Coins</h3>
            <div class="form-group">
                <div class="input-group">
                    <span class="input-group-addon"><span class="glyphicons glyphicons-lock"></span></span>
                    <input type="text" id="emp_id" name="sender" class="form-control" placeholder="Enter Your Wallet Key" value="<?php echo $row['userCoins']; ?>" maxlength="15" />
                    <span class="text-danger"><?php echo $error; ?></span>
                </div>
            </div>
            <div class="form-group">
                <button type="submit" class="btn btn-block btn-primary" name="btn-signup">Sign Up</button>
            </div>
        </center>
    </body>
</html>
<?php ob_end_flush(); ?>

```