File uploads from dynamic path

gistfile1.php

/**
 * Custom upload directory paths
 * 
 * The array keys must match the ID from exp_upload_prefs
 */
$env_config['upload_preferences'] = array(
    1 => array(
        'name'        	=> 'Assets',
        'server_path' 	=> $base_path . '/assets/',
        'url'         	=> $base_url . '/assets/',
        'allowed_types' => 'all' // 'img' or 'all'
    )
);