[want to unfavorite and item from the user's favorite list through php]

I have a server script with which i have allowed the user to mark any item as favorite, but i also want another script through which the user can unfavorite the same item if they want and that item should be deleted from their favorite list. I have kept the same table for both favorite and unfavorite code, therefore i have used update query to update the details. For this purpose i have a code, but its not working, as i am new in the programming field would appreciate if someone could provide the correct codes

 
<?php
require_once('config.php');

$favorite = $_REQUEST['favorite'];

    $unfavorite = $_REQUEST['unfavorite'];

    $id=$_REQUEST['id'];

    

$unfavoritedeal=mysql_query("SELECT * FROM favoritedeals where id='".$id."'"); //favoritedeals is the name of the table



if($row=mysql_fetch_array($unfavoritedeal))

     {

     $favorite=$row['favorite'];

     $unfavorite=$row['unfavorite'];

}



$myfavorite=(isset($_REQUEST['favorite'])?$_REQUEST['favorite']:$favorite);

         $myunfavorite=(isset($_REQUEST['unfavorite'])?$_REQUEST['unfavorite']:$unfavorite);

        

$update = mysql_query("update favoritedeals set favorite = '".$myfavorite."', unfavorite = 1 where id = '".$id."'");    



if(unfavorite="1" where id='".$id."')

{

"delete from favoritedeals WHERE id= '".$id."'";

}    





$posts[0]['message'] = 'favorite list updated';

    $selectt = mysql_query("select * from favoritedeals where id = '".$id."'");

    $results = mysql_fetch_assoc($selectt);

    $posts[0]['detail'] = $results;

    header('Content-type: application/json');

    echo json_encode($posts);

?>