$re = '/\<li\>[^<]*?(Fandoms).*?\<\/li\>/s';
$str = '<p>by <a rel="author" href="/users/Ellixerff/pseuds/Ellixerff">Ellixerff</a></p>
<p>It\'s happened before, but this time is different. Can the consequences of bringing the one you love back, cost you ev fin story.</p>
<p>Words: 8003, Chapters: 7/7, Language: English</p>
<ul>
<li>Fandoms: <a full_pat class="tag" href="https://archiveofourown.org/tags/Xena:%20Warrior%20Princess/works">Xeni Princess</a></li>
<li>Rating: <a full_path="true" class="tag" href="https://archiveofourown.org/tags/Mature/works">Mature</a></li>
<li>Warnings: <a full_f class="tag" href="https://archiveofourown.org/tags/Choose"> Chose Not To Use Archive Warnings</a></li>
<li>Categories: <a full_path="true" class="tag" href="https://archiveofourown.org/tags/F*s*F/works">F/F</a></li>
<li>Characters: <a full_path="true" href="https://archiveofourown.org/tags/Gabrielle%20(Xena)/works">Gabrielle (Xena)</a></li>
<li><a fi class="tag" href="https://archiveofourown.org/tags/Xena%20(Xena)/works">Xena (Xena)</a></li>
<li>Relationships: <a full_path="true" class="tag" href="https://archiveofourown.org/tags/Gabrielle*s*Xena/works">Gabrielle/Xena</a></li>
</ul>
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php