$re = '/(?P<nodeOpen><a:(?P<nodeName>.*)>)(?P<data>.*)(?P<nodeClose><\/a:(?P=nodeName)>)/s';
$str = '<a:b>
<a:c></a:c>
<a:c></a:c>
</a:b>';
preg_match($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