$re = '/<ul class=\"itens\"><li class=\".*?\">(.*?)<\/li><\/ul>/s';
$str = '<div class="boxAssistir"><h2 class="titulo">Selecione o Player desejado para Assistir</h2><ul class="itens"><li class="video1"><div class="icon"><div class="symbol"></div></div>OpenLoad</li><li class="video2"><div class="icon"><div class="symbol"></div></div>Ok</li><li class="video3"><div class="icon"><div class="symbol"></div></div>Streamin</li><li class="video4"><div class="icon"><div class="symbol"></div></div>Vidzi</li></ul><ul class="videos"><li class="video1-code"><iframe src="https://openload.co/embed/mGJOi4WB9uU/" scrolling="no" frameborder="0" width="538" height="408" allowfullscreen="true" webkitallowfullscreen="true" mozallowfullscreen="true"></iframe></li><li class="video2-code"><iframe width="538" height="408" data-src="http://ok.ru/videoembed/83266570810" frameborder="0" allowfullscreen></iframe></li><li class="video3-code"><iframe data-src="http://streamin.to/embed-d0i8to43pywp-538x408.html" width="538" height="408" frameborder="0" scrolling="no"></iframe></li><li class="video4-code"><iframe data-src="http://vidzi.tv/embed-n6ssttynwolm-538x408.html" width="538" height="408" frameborder="0" scrolling="no"></iframe></li></ul></div>';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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