Codeigniter - Call to undefined function mysqli_connect ()

I'm using CI in version 2.2.5 and I'm having an error in my project.

  

Error: Fatal error: Uncaught Error: Call to undefined function mysqli_connect () in C: \

     

local: system \ database \ drivers \ mysqli \ mysqli_driver.php on line 77

File function, line 77 mysqli_driver.php

function db_connect()
{
    if ($this->port != '') {
        return @mysqli_connect($this->hostname, $this->username, $this->password, $this->database, $this->port);
    } else {
        return @mysqli_connect($this->hostname, $this->username, $this->password, $this->database);
    }
}

I'm using php 7.

Does anyone know how to solve this? Thanks

Detail: I already enabled my extension=php_mysqli.dll in php.ini

In the config / database.php file I have already changed to $db['default']['dbdriver'] = 'mysqli';

But the error continues