$pattern - a string containing the pattern to search the directory for.
$dirpath - a string containing the directory path to search.
$pattern_type - a string containing the type of pattern matching functions to use (can either be 'php' or 'perl').
The format of the $pattern depends on the $pattern_type-value. If this value is 'php', then the pattern has to follow the conventions of the eregi_*-functions, else if the value 'perl', then follow the preg_*-patternformat. It is recommanded to use 'perl', because this is faster.