$re = '/<a[^>]*?href=(["\'])?((?:.(?!\1|>))*.?)\1?/i';
$str = '<li class="navItem "><a href="/services/" lang="de" hreflang="de">Services</a></li>
<a class="iMacLink" href="/portfolio/" ><div class="iMacOverlay"></div><div class="">Super</div></a></div>
<div class="addthis_toolbox addthis_default_style">
<a itemprop="url" target="_blank" href="https://www.facebook.com/any-profile" title="facebook" class="facebookSite"><span class="icon-facebook"></span></a>
<a itemprop="url" target="_blank" href="https://twitter.com/any-profile" title="twitter" class="twitterSite"><span class="icon-twitter"></span></a>
<a itemprop="url" target="_blank" href="https://pinterest.com/any-profile" title="pinterest" class="pinterestSite"><span class="icon-pinterest"></span></a>
<a itemprop="url" target="_blank" href="//feeds.feedburner.comany-profile?format=xml" title="rss" class="rss"><span class="icon-rss"></span></a>
</div>
<a class="social facebookProfil" href="http://www.facebook.com/any-profile">Facebook</a>
<a class="social facebookProfil" href=\'https://www.facebook.com/single-quotes\'>Facebook</a>
<a class="social facebookProfil" href=https://www.facebook.com/no-quotes>Facebook</a>
<a class="social youtubeProfil" href="http://www.youtube.com/user/any-profile">Youtube</a>
<a class="social vimeoProfil" href="http://vimeo.com/any-profile">Vimeo</a>
<a class="social xingProfil" href="https://www.xing.com/companies/any-profile">XING</a>
<a class="social twitterProfil" href="https://twitter.com/any-profile">Folge bei Twitter</a>
<a href="https://www.instagram.com/p/CN-Kx40nOW0/">Instagram Beitrag</a>
<a href="http://instagram.com/quellenhofaachen">Instagram Profil</a>
<a href="https://www.instagram.com/explore/tags/url">Instagram Tag-Url</a>
<A href="https://www.Instagram.com/uppercase-link">Upercase-link</A>
<a href="http://instagram.com/unique">Unique-test http</a>
<a href="//instagram.com/unique">Unique-test protocol relative</a>
<a href="https://instagram.com/unique">Unique-test https</a>
<a href="http://www.instagram.com/unique">Unique-test www</a>
';
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