php - PHP htmlentitiesで許可されているのは、

Answer 1

とても簡単です

<?php
$string = htmlentities($text);
$string = str_replace(array("&lt;i&gt;", "&lt;b&gt;", "&lt;/i&gt;", "&lt;/b&gt;"), array("<i>", "<b>", "</i>", "</b>"), $string);

Answer 2

ヘルパー関数を使用します：

#   Sanitizer function - removes forbidden tags, including script tags
function strip_tags_attributes( $str, 
    $allowedTags = array('<a>','<b>','<blockquote>','<br>','<cite>','<code>','<del>','<div>','<em>','<ul>','<ol>','<li>','<dl>','<dt>','<dd>','<img>','<ins>','<u>','<q>','<h3>','<h4>','<h5>','<h6>','<samp>','<strong>','<sub>','<sup>','<p>','<table>','<tr>','<td>','<th>','<pre>','<span>'), 
    $disabledEvents = array('onclick','ondblclick','onkeydown','onkeypress','onkeyup','onload','onmousedown','onmousemove','onmouseout','onmouseover','onmouseup','onunload') )
{       
    if( empty($disabledEvents) ) {
        return strip_tags($str, implode('', $allowedTags));
    }
    return preg_replace('/<(.*?)>/ies', "'<' . preg_replace(array('/javascript:[^\"\']*/i', '/(" . implode('|', $disabledEvents) . ")=[\"\'][^\"\']*[\"\']/i', '/\s+/'), array('', '', ' '), stripslashes('\\1')) . '>'", strip_tags($str, implode('', $allowedTags)));
}

たとえば、配列以外のすべてを配列から削除<b>し<i>ます$allowedTags。