Fix "Error: Invalid file" error in Pico Admin plugin when running Pico in subfolder.

pico_editor.php

	private function do_open()
	{
		if(!isset($_SESSION['pico_logged_in']) || !$_SESSION['pico_logged_in']) die(json_encode(array('error' => 'Error: Unathorized')));
		$file_url = isset($_POST['file']) && $_POST['file'] ? $_POST['file'] : '';

		$script_name = $_SERVER['SCRIPT_NAME'];
		$sub_folder = str_replace('/index.php', '', $script_name);

		if ($sub_folder != '')
		{
			$file = substr($file_url, strpos($file_url, $sub_folder) + strlen($sub_folder));
		}
		else
		{
			$file = basename(strip_tags($file_url));
		}

		if(!$file) die('Error: Invalid file');
		$file .= CONTENT_EXT;
		if(file_exists(CONTENT_DIR . $file)) die(file_get_contents(CONTENT_DIR . $file));
		else die('Error: Invalid file');
	}
	
	private function do_save()
	{
		if(!isset($_SESSION['pico_logged_in']) || !$_SESSION['pico_logged_in']) die(json_encode(array('error' => 'Error: Unathorized')));
		$file_url = isset($_POST['file']) && $_POST['file'] ? $_POST['file'] : '';

		$script_name = $_SERVER['SCRIPT_NAME'];
		$sub_folder = str_replace('/index.php', '', $script_name);

		if ($sub_folder != '')
		{
			$file = substr($file_url, strpos($file_url, $sub_folder) + strlen($sub_folder));
		}
		else
		{
			$file = basename(strip_tags($file_url));
		}

		if(!$file) die('Error: Invalid file');
		$content = isset($_POST['content']) && $_POST['content'] ? $_POST['content'] : '';
		if(!$content) die('Error: Invalid content');
		
		$file .= CONTENT_EXT;
		file_put_contents(CONTENT_DIR . $file, $content);
		die($content);
	}
	
	private function do_delete()
	{
		if(!isset($_SESSION['pico_logged_in']) || !$_SESSION['pico_logged_in']) die(json_encode(array('error' => 'Error: Unathorized')));
		$file_url = isset($_POST['file']) && $_POST['file'] ? $_POST['file'] : '';

		$script_name = $_SERVER['SCRIPT_NAME'];
		$sub_folder = str_replace('/index.php', '', $script_name);

		if ($sub_folder != '')
		{
			$file = substr($file_url, strpos($file_url, $sub_folder) + strlen($sub_folder));
		}
		else
		{
			$file = basename(strip_tags($file_url));
		}

		if(!$file) die('Error: Invalid file');
		
		$file .= CONTENT_EXT;
		if(file_exists(CONTENT_DIR . $file)) die(unlink(CONTENT_DIR . $file));
	}