$re = '/href="(.*?)".*Контакты<\/a>/';
$str = '<li class="b-index-nav__item"><a href="/work/" class="b-index-nav__link">Портфолио</a></li><li class="b-index-nav__item"><a href="/jobs/" class="b-index-nav__link">Вакансии</a></li><li class="b-index-nav__item"><a href="/contact/" rel="nofollow" class="b-index-nav__link">Контакты</a></li>';
preg_match_all($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