PHP接続oracle

function connect_oracle(){

    

    static $dbconn = false;

    if(!$dbconn){

        $db_server = "127.0.0.1";

        $db_user = "zzzz";

        $db_pass = "zzzzzz123";

        $db_sid = "MBDWV2";

        $dbconn = OCILogon($db_user,$db_pass,"(DESCRIPTION =

                  (ADDRESS_LIST =

                      (ADDRESS = (PROTOCOL = TCP)(HOST = {$db_server})(PORT = 1521))

                    )

                    (CONNECT_DATA =

                      (SERVICE_NAME = {$db_sid})

                    )

                  )","utf8");

        if($dbconn==false)

           die("    oracle");

    }

    return $dbconn;

}