$re = '/([0-9a-f]{32}){1,2}/';
$str = 'Success: Feed File Uploaded. Use the reference code afc3d6e84df84f51944a06cccee8f59a to track these records in the logs.';
preg_match($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