$re = '/<\/?Reference.*\/?>/m';
$str = '<Reference Include="Microsoft.AspNetCore.Sockets.Common.Http, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60, processorArchitecture=MSIL">
<HintPath>..\\..\\packages\\LIB.XPTO.1.18.524.20\\lib\\net45\\Microsoft.AspNetCore.Sockets.Common.Http.dll</HintPath>
</Reference>
<Reference Include="Microsoft.CSharp" />
<Reference Include="Microsoft.Extensions.Configuration.Abstractions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60, processorArchitecture=MSIL">
<HintPath>..\\..\\packages\\LIB.XPTO.1.0.1.2\\lib\\net45\\Microsoft.Extensions.Configuration.Abstractions.dll</HintPath>
</Reference>';
preg_match_all($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