####################### getUsers.php file ############################

<?php

/** MySQL settings **/
/** The name of the database for WordPress **/
define('DB_NAME', 'test_db');
/** MySQL database username */
define('DB_USER', 'testuser');
/** MySQL database password */
define('DB_PASSWORD', 'testpass');
/** MySQL hostname */
define('DB_HOST', 'localhost');

require_once('application/classes/database.php');

function die_r($value)
{
    echo '<pre>';
    print_r($value);
    echo '</pre>';
    die();
}


$db = new Database();

$getRow = $db->getRow("SELECT * FROM users WHERE userID = ?", ["1"]);

die_r($getRow);

######################  database.php file ###############################
<?php

/******  SETUP DATABASE CLASS ******/

class Database {

    /***  CONNECT TO THE DATABASE  ***/
    public $isConnected;
    protected $datab;

    public function __construct($dbhost = DB_HOST, $dbname = DB_NAME, $dbuser = DB_USER, $dbpass = DB_PASSWORD)
                {
        $this->isConn = TRUE;

        try{
                        $this->datab = new PDO ( "mysql:host={$dbhost};dbname={$dbname};charset=utf8", $dbuser, $dbpass);
            $this->datab->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
            $this->datab->setAttribute( PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC );
        } catch ( PDOException $e ) {
            $this->isConn = FALSE;
            throw new Exception ($e->getMessage () );
        }
    }

    /***  DISCONNECT FROM DATABASE  ***/

    public function Disconnect(){
        $this->datab = NULL;
        $this->isConn = FALSE;
    }

    /***  GET ROW  ***/

    public function getRow($query, $params = []){
            try {
                $stmt = $this->datab->prepare($query);
                $stmt->execute($params);
                return $stmt->fetch();
            } catch ( PDOException $e ) {
                throw new Exception ($e->getMessage () );
            }
    }
}