Вроде все правильно.А ошибку найти не могу, подскажите пожалуйста где ошибка.

<?php
  require_once "config.php";
  
  class db extends config {
  
  private $connection;
  
  function _construct() {
  
   $this->open_connection();
  //echo "connection is set";
  }
  
  private function open_connection() {
     $this->connection = mysql_connect($this->DB_HOST,$this->DB_USER,$this->DB_PASS);
         if(!$this->connection) {
         die("Db con fail" .mysql_error());
         } else {
         $db_select = mysql_select_db($this->DB_NAME);
         if(!$db_select) {
         die("fail".mysql_error());
         }
         }
    mysql_query("set name utf8") or die("set names utf8 failed");
  }

    public function sql($query) {
	   $result = mysql_query($query,$this->connection);
	   if(!$result) {
	        die("Database query failed: ".mysql_error());
	    }
	return $result;
	} 
   
   
  }
  $db = new db();
?>