If a file with the same name exist and is writable, it is replaced
by the new tar.
The method return false and a PEAR error text.
The $p_filelist parameter can be an array of string, each string
representing a filename or a directory name with their path if
needed. It can also be a single string with names separated by a
single blank.
For each directory added in the archive, the files and
sub-directories are also added.
See also createModify() method for more details.