$re = '/<button[^<]*>.*[\s\S]*<\/button>|<iframe[^<>]*\/>|<tr>[^<td>]*<\/tr>/';
$str = '<table width="30px">
<P>Teste</p><iframe src="teste" /><p>Test</p>
<div><span>Teste Regex</span></div>
<p>Test</p><button onclick="myFunction()">Click me</button>
<table>
<tr><td>34</td></tr>>
</table>';
preg_match_all($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