PHP MySQL not inserting data into the database and returning product id as 0 -

i cant seem function enter data database , return product_id. when try returning product_id returns 0 along nothing entered database

php function:

function product_id(){     $id_data = "insert `products` (`product_id`, `date_created`) values('', now())";      mysqli_query(database(), $id_data);      return $product_id = mysqli_insert_id(database()); } 

mysql

create table products( product_id int unsigned not null auto_increment, date_created datetime not null, primary key (product_id) ); 

here how call function in php

$product_id = product_id(); 

since cannot insert auto_increment field remove insert statement , should work.

function product_id(){     $id_data = "insert `products` (`date_created`) values( now())";      mysqli_query(database(), $id_data);      return $product_id = mysqli_insert_id(database()); } 

also getting mysqli error in future try using mysqli_error() function

http://php.net/manual/en/mysqli.error.php