警告：mysqli_query（）要求参数1为mysqli，在第19行的Operations.php中给出null

I have Connection class and Operations class when call the required method which is used to insert the record to the database , that shows the error.

File Name : Connection.php

<?php
/**
* Connection class to make "connection" with database
*/
class Connection  
{   
    public $host;
    public $user;
    public $password;
    public $databaseName;

    /**
    * Constructor
    */
public  function __construct()
    {   
        $this->host = '';
        $this->user = '';
        $this->password = '';
        $this->databaseName = '';

        $this->connect();
    }
    /**
    * The method that make the connection to the database
    */

Connection method which is used to establish the connection

    public function connect()
    {
        $con = mysqli_connect($this->host, $this->user, $this->password, $this->databaseName);
        if(!$con){
            echo "Connect to the database failed";
        }

        return $con;
    }

}

FIle Name : Operations.php

 require_once"Connection.php";

    class Operations
    {
        //$Connection = new Connection();
        //$con = $Connection->connect();
        function __construct()
        {
            $Connection = new Connection();
            $con = $Connection->connect();
        }

When i call this following function, it's show me the error

        public function add_main_menu($title, $title_ara, $image)
        {
            $sql = "INSERT INTO menu (title, title_ara, image) VALUES ('$title', '$title_ara', '$image')";
            $result = mysqli_query($con, $sql);

            return $result;
        }

        public function add_sub_menu($title, $title_ara, $price, $description, $descreption_ara, $image, $menu_id){

            $sql = "INSERT INTO sub_menu (title, title_ara, price, description, description_ara, image, menu_id) VALUES ('$title', '$title_ara', $price, '$description', '$description_ara', '$image', '$menu_id')";
            $result = mysqli_query($con, $sql);

            return $result;
        }
    }

Change the Connection.php as following,

<?php
class Connection  
{   
    public $host;
    public $user;
    public $password;
    public $databaseName;

public  function __construct($host,$user,$password,$database)
    {   
        $this->host = $host;
        $this->user = $user;
        $this->password = $password;
        $this->databaseName = $database;

        $this->connect();
    }

Now change the Operations.php file as following

 require_once"Connection.php";
    class Operations
    {
        function __construct()
        {
            $Connection = new Connection("host","user","passwrd","database");
            $con = $Connection->connect();
        }