<?php

$string = '<a href="/path/to/file?a=b&foo=bar#baz">';
$string = htmlentities($string, ENT_QUOTES, 'UTF-8', false);
$strng = htmlentities($string, ENT_QUOTES, 'UTF-8', false);
var_dump($string); //stored in database

$string = html_entity_decode($string, ENT_QUOTES, 'UTF-8');
var_dump($string); //output from database