我想在另一个类中使用另一个类的函数，而不是每次使用它时都将它发送到变量

Question

The class I want to use use the variable in is like so:

Class OrdersModel extends DatabaseFactory
{
    public function userownsorder($id, $buysell) 
    {
        //sql to run
        $sql = "SELECT count(*) FROM orders 
                WHERE id = ? 
                AND user = ? 
                AND buysell = 'buy'";

        //run the sql
        $checkfield = $database->prepare($sql);
        $checkfield->execute(array($id, Session::get('id')));

        //return the results
        return $checkfield->fetchColumn();


    }

But each time I want to use the database I need to iniate it like so:

$database = DatabaseFactory::getFactory()->getConnection();

in each function which is a bit repetative and will bloat my files, is there a way to use the $database without iniating it each time, I have tried the following:

global $database = DatabaseFactory::getFactory()->getConnection();  

and:

function __construct()
{
    $database = DatabaseFactory::getFactory()->getConnection(); 
}

but neither work, I don't really want to use $this->database but would rather just use the variable $database.... here is the database class:

<?php

class DatabaseFactory
{
    private static $factory;
    private $database;

    public static function getFactory()
    {
        if (!self::$factory) {
            self::$factory = new DatabaseFactory();
        }
        return self::$factory;
    }

    public function getConnection() {
        if (!$this->database) {

            /**
             * Check DB connection in try/catch block. Also when PDO is not constructed properly,
             * prevent to exposing database host, username and password in plain text as:
             * PDO->__construct('mysql:host=127....', 'root', '12345678', Array)
             * by throwing custom error message
             */
            try {
                $options = array(PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ, PDO::ATTR_ERRMODE => PDO::ERRMODE_WARNING);
                $this->database = new PDO(
                   Config::get('DB_TYPE') . ':host=' . Config::get('DB_HOST') . ';dbname=' .
                   Config::get('DB_NAME') . ';port=' . Config::get('DB_PORT') . ';charset=' . Config::get('DB_CHARSET'),
                   Config::get('DB_USER'), Config::get('DB_PASS'), $options
                   );
            } catch (PDOException $e) {

                // Echo custom message. Echo error code gives you some info.
                echo 'Database connection can not be estabilished. Please try again later.' . '<br>';
                echo 'Error code: ' . $e->getCode();

                // Stop application :(
                // No connection, reached limit connections etc. so no point to keep it running
                exit;
            }
        }
        return $this->database;
    }
}