Fatal error: Uncaught mysqli_sql_exception: Duplicate entry '4' for key 'cart_details.PRIMARY' in /var/www/html/functions/common_function.php:313 Stack trace: #0 /var/www/html/functions/common_function.php(313): mysqli_query(Object(mysqli), 'insert into `ca...') #1 /var/www/html/index.php(17): cart() #2 {main} thrown in /var/www/html/functions/common_function.php on line 313