Most efficient way to detect a set of words in a text without regex
<p>Unfortunately, for some strange reason the regex method isn't working for me with UTF-8 (<a href="http://stackoverflow.com/questions/10063874/preg-replace-utf-8-doesnt-work-on-one-server-but-works-on-another">preg_replace + UTF-8 doesn&#39;t work on one server but works on another</a>).</p>

<p>What would be the most efficient way to accomplish my goal without using regex?</p>

<p>Just to make it as clear as possible, for the following set of words:<br>
cat, dog, sky</p>

<p>cats would return false<br>
the sky is blue would return true<br>
skyrim would return false</p>
