Insert

//Create a folder in you directory call it settings
//Inside it create a file call it db_connection_setting.ini
//Inside the file write below code

host = localhost
schema = name_of_your_database
username = database_username
password = database_password
charset = utf8


//Create Connection Class Call it dbConn.php

class dbConn {


    private $file_settings = 'settings/db_connection_setting.ini';
    public $conn;

    // get the database connection
    public function getConnection(){
        $this->conn = null;
        if (!$settings = parse_ini_file($this->file_settings, TRUE)) throw new exception('Unable to open ' . $this->file_settings . '.');
        $dsn = "mysql:host=".$settings['host'].";dbname=".$settings['schema'].";charset=".$settings['charset']."";
        $opt = [
            PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES   => false,
        ];
        try{
            $this->conn = new PDO($dsn,$settings['username'], $settings['password'], $opt);
        }catch(PDOException $exception){
            echo "Connection error: " . $exception->getMessage();
        }
        return $this->conn;
    }

}


//Create a function class file call it product.php
// now inside this file paste below code

class product {
    // database connection and table name
    private $con;

    // object properties
    public function __construct($db){
        $this->con = $db;
    }

public function getProductFromURL($id){

     // Better to use $stmt as the variable here, obviously this is subjective
     // but will serve you better when you are working on other stmt objects
     $stmt = $this->con->prepare("SELECT * FROM product_table WHERE product_id = :product_id ORDER BY ID");
     $stmt->bindParam(':product_id', $id,PDO::PARAM_INT);
     $stmt->execute();

     $results = $stmt->fetchAll(PDO::FETCH_OBJ);
     return $results;
}

}


//Then to make use of this function inside your file call it this way
include_once 'dbConn.php';

// instantiate database and objects
$data = new dbConn ();
$db = $data->getConnection();
$get_product = new product($db);
$get_product_by_id = $get_product->getProductFromURL($_GET['pid']);