$re = '/\/A\/B\/C\/D\/([^\/]+)\/(\w+)?(?:\.(\w+))?\.(?:log|trc)/m';
$str = '/A/B/C/D/TEXT1/TEXT2.TEXT3.log
/A/B/C/D/TEXT1/TEXT2.trc';
preg_match_all($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