Function Name must be A String

I am trying to get comments from users but the browser says The Whole Php Fatal Error: Function name must be a string in .......... in line 49.My code;

Php Code

<?php

namespace Revolution;
if(!defined('IN_INDEX')) { die('Sorry, you cannot access this file.'); }
class engine
{
        private $initiated;
        private $connected;
        
        private $connection;
        
        
        final public function Initiate()
        {
                global $_CONFIG;
                if(!$this->initiated)
                {
                        $this->setMySQL('connect', mysql_connect);
                        $this->setMySQL('pconnect', mysql_pconnect);
                        $this->setMysql('select_db', mysql_select_db);
                        $this->setMySQL('query', mysql_query);
                        $this->setMySQL('num_rows', mysql_num_rows);
                        $this->setMySQL('fetch_assoc', mysql_fetch_assoc);
                        $this->setMySQL('fetch_array',mysql_fetch_array);
                        $this->setMySQL('result', mysql_result);
                        $this->setMySQL('free_result', mysql_free_result);
                        $this->setMySQL('escape_string', mysql_real_escape_string);
                        
                        $this->initiated = true;
                
                        $this->connect($_CONFIG['mysql']['connection_type']);
                }
        }
        
        final public function setMySQL($key, $value)
        {
                $this->mysql[$key] = $value;
        }
        
        
        /*-------------------------------Manage Connection-------------------------------------*/
        
        final public function connect($type)
        {
                global $core, $_CONFIG;
                if(!$this->connected)
                {
            $func = $this->mysqli[$type];
            $this->connection = $func($_CONFIG['mysqli']['localhost'], $_CONFIG['mysqli']['root'], $_CONFIG['mysqli']['adventurer']);
                        
                        if($this->connection)
                        {
                                $mydatabase = $func['Habboretro']($_CONFIG['mysql']['Habboretro'], $this->connection);
                                
                                if($mydatabase)
                                {
                                        $this->connected = true;     
                                }
                                else
                                {
                                        $core->systemError('MySQL Engine', 'MySQL could connect to database');
                                }
                        }
                        else
                        {
                                $core->systemError('MySQL Engine', 'MySQL could connect to host');                   
                        }
                }
        }
        
        final public function disconnect()
        {
                global $core;
                if($this->connected)
                {
                        if($this->mysql['close'])
                        {
                                $this->connected = false;
                        }
                        else
                        {
                                $core->systemError('MySQL Engine', 'MySQL could not disconnect.');
                        }
                }
        }
        
        /*-------------------------------Secure MySQL variables-------------------------------------*/
        
        final public function secure($var)
        {
                return $this->mysql['escape_string'](stripslashes(htmlspecialchars($var)));
        }
        
        /*-------------------------------Manage MySQL queries-------------------------------------*/
        
        final public function query($sql)
        {
                return $this->mysql['query']($sql, $this->connection) or die(mysql_error());
        }
        
        final public function num_rows($sql)
        {
                return $this->mysql['num_rows']($this->mysql['query']($sql, $this->connection));
        }
        
        final public function result($sql)
        {
                return $this->mysql['result']($this->mysql['query']($sql, $this->connection), 0);
        }
        
        final public function free_result($sql)
        {
                return $this->mysql['free_result']($sql);
        }
        
        final public function fetch_array($sql)
        {
                $query = $this->mysql['query']($sql, $this->connection);
                
                $data = array();
                
                while($row = $this->mysql['fetch_array']($query))
                {
                        $data[] = $row;
                }
                
                return $data;
        }
        
        final public function fetch_assoc($sql)
        {
                return $this->mysql['fetch_assoc']($this->mysql['query']($sql, $this->connection));
        }




}
?>

Row 49.

    $this->connection = $func($_CONFIG['mysqli']['localhost'], $_CONFIG['mysqli']['root'], $_CONFIG['mysqli']['adventurer']);

been finding answers for about 5 days