Rod med funktion

PHP kode 

 <?php 
 class model {
     $this->DB_NAME = 'DATABASE_NAME';
     $this->DB_HOST = 'DATABASE_HOST';
     $this->DB_USER = 'DATABASE_USER';
     $this->DB_PASS = 'DATABASE_PASSWORD';
     
     function __construct($foo = null) {
         $this->mysqli = new mysqli($this->DB_HOST, $this->DB_USER, $this->DB_PASS, $this->DB_NAME);
         if (mysqli_connect_errno()) {
             throw new Exception("Connect failed: %s\n", mysqli_connect_error());
         }
     }
     
     function close_connection() {
         mysqli_close($this->mysqli);
     }
 }
 
 
 class page extends model {
     function __construct() {
         parent::__construct();
     }
 
     function get_page_options($page_part) {
         $stmt = $this->mysqli->prepare('SELECT `option_value` FROM `page_options` WHERE `option_name`=?');
         $stmt->bind_param('s', $page_part);
         $stmt->execute();
         $stmt->bind_result($page_option);
         $stmt->fetch();
         $stmt->close();
         return $page_option;
     }
 }