[help] [php] how to null this?

<?php include("includes/header.php");

    require("includes/function.php");
    $kwallpaper=new  k_wallpaper;
    include('purchase.php');
    
    
    if(isset($_POST['submit']))
    {
        
         if(verify_purchase($_POST['buyer'],$_POST['purchase_code']) == false)
         {
            
            $_SESSION['msg']="Sorry, we are unable to verify your purchase.";
            header( "Location:app_verify.php");
            exit;
        }
        else
        {
             $data = array(
            'buyer'  =>  $_POST['buyer'],
            'purchase_code' => $_POST['purchase_code'],
            'status' => '1'
            );
          
            $app_edit=Update('app_verify', $data, "WHERE id = '1'");
            
            if ($app_edit > 0){
                
                $_SESSION['msg']="Save successfully...";
                header( "Location:app_verify.php");
                exit;
            }     
        }
        
        
        
    }
    //Get Data
    $app_qry="SELECT * FROM app_verify WHERE id='1'";
    $app_result=mysql_query($app_qry);
    $app_row=mysql_fetch_assoc($app_result);
    
?>
    
    
<script src="js/category.js" type="text/javascript"></script> 
                
                <div id="main">
                <h2><a href="home.php">Dashboard</a> &raquo; <a href="#" class="active"></a></h2>
                <?php if(isset($_SESSION['msg'])!= '')
                {
                echo '<p style="color:white">'.$_SESSION['msg'].'</p>';
                $_SESSION['msg'] = '';   
                }
                ?>
                    <form action="" name="addeditcategory" method="post" class="jNice" onsubmit="return checkValidation(this);" enctype="multipart/form-data">
                    
                                            
                    <h3>App Verify</h3>
                        <fieldset>
                        
<label>Buyer:</label>
                                
      
                                
                             <input type="text" name="buyer" id="buyer" value="<?php echo $app_row['buyer'];?>" >
                            <label style="padding-top:20px;">Purchase Code</label>
                         <input type="text" name="purchase_code" id="purchase_code" value="<?php echo $app_row['purchase_code'];?>" > 
                         <p></p>
           <input type="submit" name="submit" value="Save" />
                        
                        </fieldset>
                    </form>
                </div>
                <!-- // #main -->
                
                <div class="clear"></div>
            </div>
            <!-- // #container -->
        </div>   
        <!-- // #containerHolder -->
        
<?php include("includes/footer.php");?>

<?php error_reporting(0);
/*
     * Item purchase verification by envato api
     */
    function verify_purchase($buyer_name,$p_code)
    {
        
        
        $envato_username = "viaviwebtech";
        $envato_api_key  = "2uw51mxa55u4dsxh8m8a4i7bqp4ux1p0";
        
        $buyer                =    $buyer_name;
        $purchase_code        =    $p_code;
        
        $curl                 =    curl_init('http://marketplace.envato.com/api/edge/'.$envato_username.'/'.$envato_api_key.'/verify-purchase:'.$purchase_code.'.xml');
        
        curl_setopt($curl, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT'] );
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($curl, CURLOPT_TIMEOUT, 30);
        curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 1);
        
        $purchase_data        =    curl_exec($curl);
        curl_close($curl);
        
        
        $purchase_data        =    json_decode(json_encode((array) simplexml_load_string($purchase_data)),1);

        if ( isset($purchase_data['verify-purchase']['buyer']) && $purchase_data['verify-purchase']['buyer'] == $buyer)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    
    function purchase_status()
    {
        $app_qry="SELECT * FROM app_verify WHERE id='1'";
        $app_result=mysql_query($app_qry);
        $app_row=mysql_fetch_assoc($app_result);
        
        if($app_row['status']=='1')
        {
            return true;
        }
        else
        {
            return false;
        }
    }
 
?>