<?php
$str = '<html>
<body>
<![CDATA[
alert alert
]]>
<h1> This is the title </h1>
<!--
alert
alert
-->
<p> some description text here, <b>this</b> is a word. </p>
</body>
</html>';
print_r(array_count_values(str_word_count(strip_tags(strtolower($str)), 1)));
?>