$re = '/(?s)<data name="([^"]*)">(?:(?!data).)*DoNotUse/m';
$str = '<data name="A">
<value>A</value>
<comment>Bla Bla</comment>
</data>
<data name="B">
<value>B</value>
</data>
<data name="C">
<value>###DoNotUse###</value>
<comment>Bla Bla</comment>
</data>
<data name="D">
<value>D</value>
<comment>Bla Bla</comment>
</data>
<data name="E">
<value>###DoNotUse###</value>
</data>';
preg_match_all($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