MY_html_helper.php

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

if ( ! function_exists('file_digest'))
{
	/**
	 * File digest
	 *
	 * Creates a base64-encoded hash of a file for a subresource integrity
	 * check 
	 *
	 * @param	string
	 * @param	string
	 * @return	string
	 */
	function file_digest($file, $hash_function = 'sha256')
	{
		$file_contents = file_get_contents($file);
		$hash = hash($hash_function, $file_contents, true);
		$encoded_hash = base64_encode($hash);

		return $hash_function.'-'.$encoded_hash;
	}
}