system/helpers/security_helper.php

<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2017, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package	CodeIgniter
 * @author	EllisLab Dev Team
 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright	Copyright (c) 2014 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
 * @license	http://opensource.org/licenses/MIT	MIT License
 * @link	https://codeigniter.com
 * @since	Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * CodeIgniter Security Helpers
 *
 * @package		CodeIgniter
 * @subpackage	Helpers
 * @category	Helpers
 * @author		EllisLab Dev Team
 * @link		https://codeigniter.com/user_guide/helpers/security_helper.html
 */

// ------------------------------------------------------------------------

if ( ! function_exists('xss_clean'))
{
	/**
	 * XSS Filtering
	 *
	 * @param	string
	 * @param	bool	whether or not the content is an image file
	 * @return	string
	 */
	function xss_clean($str, $is_image = FALSE)
	{
		return get_instance()->security->xss_clean($str, $is_image);
	}
}

// ------------------------------------------------------------------------

if ( ! function_exists('sanitize_filename'))
{
	/**
	 * Sanitize Filename
	 *
	 * @param	string
	 * @return	string
	 */
	function sanitize_filename($filename)
	{
		return get_instance()->security->sanitize_filename($filename);
	}
}

// --------------------------------------------------------------------

if ( ! function_exists('do_hash'))
{
	/**
	 * Hash encode a string
	 *
	 * @todo	Remove in version 3.1+.
	 * @deprecated	3.0.0	Use PHP's native hash() instead.
	 * @param	string	$str
	 * @param	string	$type = 'sha1'
	 * @return	string
	 */
	function do_hash($str, $type = 'sha1')
	{
		if ( ! in_array(strtolower($type), hash_algos()))
		{
			$type = 'md5';
		}

		return hash($type, $str);
	}
}

// ------------------------------------------------------------------------

if ( ! function_exists('strip_image_tags'))
{
	/**
	 * Strip Image Tags
	 *
	 * @param	string
	 * @return	string
	 */
	function strip_image_tags($str)
	{
		return get_instance()->security->strip_image_tags($str);
	}
}

// ------------------------------------------------------------------------

if ( ! function_exists('encode_php_tags'))
{
	/**
	 * Convert PHP tags to entities
	 *
	 * @param	string
	 * @return	string
	 */
	function encode_php_tags($str)
	{
		return str_replace(array('<?', '?>'), array('&lt;?', '?&gt;'), $str);
	}
}