The following line will convert string error into a two dimensional array containing the components from the error string for each line. It will match Error, Warning, Info and Access error types. You can then do something useful with the output.
<?php
preg_match_all('/^(?:line (\d+) column (\d+) - )?(\S+): (?:\[((?:\d+\.?){4})]:)
?(.*?)$/m', $tidy->errorBuffer, $tidy_errors, PREG_SET_ORDER);
?>
And a small tip, always run the error messages through htmlentities when outputting to convert the tags in the error to a viewable form.
