$re = '/<ca>(.*?)<\/ca>|<cert>(.*?)<\/cert>/s';
$str = 'Internal Auto-Configured Settings File
________________________________________
(( Do not attempt to edit it manually ))
________________________________________
# Saved certifications:
<ca>
Text which I want to extract
</ca>
...
<cert>Another text I want to extract</cert>
...';
preg_match_all($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