$re = '/(>\s+<)/';
$str = '<ul class="list-group sidebar-nav-v1 margin-bottom-40" id="menuHomeUserPrivate">
<li class="list-group-item active">
<a id="to_ProfileOverall" class="privateMenuLinkJS"><i class="fa fa-bar-chart-o"></i> Overall</a>
</li>
<li class="list-group-item list-toggle">
<a data-toggle="collapse" data-parent="#menuHomeUserPrivate" href="#collapse-MoneyManage" ><i class="fa fa-money"></i> Invoice</a>
<ul id="collapse-MoneyManage" class="collapse">
<li><a id="to_MoneyManagerFaturamentoInsert" class="privateMenuLinkJS"><i class="fa fa-level-down"></i> Big Invoice </a></li>
<li><a id="to_MoneyManagerFaturamentoGerir" class="privateMenuLinkJS"><i class="fa fa-cogs"></i> Big big big
Invoice 2 </a></li>
</ul>
</li>
</ul>';
$subst = "><";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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