{
 "debug": {
  "db_host": "",
  "db_name": "",
  "db_user": "",
  "db_password": ""
 }
}

?php
class DbConf{
 public static function Conf( $conf_name ){
  
  if(empty($conf_name)){
   die("Illegal parameter");
  }

  $from = "localhost"; // allow legal host only
  if(!isset($_SERVER['HTTP_HOST']) || $_SERVER['HTTP_HOST']!=$from){
   die("Unauthorized access");
  }

  $json_config = file_get_contents('db-config.json');

  $json_data = json_decode($json_config, true);

  if( array_key_exists($conf_name, $json_data)){
   return $json_data[$conf_name];
  }else{
   return "Not Found";
  }
 }
}