mongodb - Custom constructor in my PHP class doesn't work -

i trying acquainted php , came across problem i'll describe now.

basically, have parent class following structure:

abstract class dbconn {     protected $con;      abstract function __construct($host, $user, $pass);     abstract function getconnectionstring($host, $user, $pass); } 

also, have child class code:

class mongodbconn extends dbconn {     private $col;      private function __construct($host, $user, $pass) {         try {             $server = self::getconnectionstring($host, $user, $pass);             $this->con = (new mongoclient($server))->selectdb('sicom');         } catch (mongoconnectionexception $ex) {             $em = 'connection error';             throw new exception($em, err_db_conn, $ex);         }     }      public function getconnectionstring($host, $user, $pass) {         return "mongodb://" . $user . ":" . $pass . "@" . $host;     } } 

this doesn't seem work. use following php test code:

// contains class mongodbconn require $_server['document_root'] . "/knl/db/dbconn-mongo.php"; // contains sicom_* values require $_server['document_root'] . "/knl/config.db.php";  $dx = new mongodbconn(sicom_db_host,sicom_db_user,sicom_db_password); var_dump($dx); 

and receive no dump, because $dx null.

i don't have enough experience php know causing problem, nor have enough nginx (the web server i'm using) know for. please me find solution?

thanks!

edit: modified code according suggestions, realized following: while test file uses 2 requires, file mongodbconn class declared uses couple more. when try use "require ...dbconn-mongo.php", main page crashes. because can't have require inside file uses require? if so, workaround? (one of required files contains return codes; 1 contains field names, , on.)

make constructor public. otherwise doesn't called @ all, , no database connection created.