Automatic extension installation

install.php

<?php
define('_JEXEC', 1);
define('DS', DIRECTORY_SEPARATOR);

if (file_exists(dirname(__FILE__) . '/defines.php')) {
        include_once dirname(__FILE__) . '/defines.php';
}

if (!defined('_JDEFINES')) {
        define('JPATH_BASE', dirname(__FILE__));
        require_once JPATH_BASE.'/includes/defines.php';
}

require_once JPATH_BASE.'/includes/framework.php';

jimport('joomla.installer.installer');
jimport('joomla.log.log');
jimport('joomla.plugin.helper');
jimport('joomla.application.component.helper');
jimport('joomla.environment.request');
jimport('joomla.application.application');

$installer = JInstaller::getInstance();

$basepath = '/home/username/extensions';
$packages = array(
        'com_whatever',
        'mod_whatever',
);

foreach($packages as $p)
        $installer->install($basepath.$p);