(PHP 5 >= 5.2.0, PECL zip >= 1.4.0)
ZipArchive::setCommentName — Set the comment of an entry defined by its name
Set the comment of an entry defined by its name.
nameName of the entry.
commentThe contents of the comment.
   Returns TRUE on success or FALSE on failure.
  
Example #1 Open an archive and set a comment for an entry
<?php
$zip = new ZipArchive;
$res = $zip->open('test.zip');
if ($res === TRUE) {
    $zip->setCommentName('entry1.txt', 'new entry comment');
    $zip->close();
    echo 'ok';
} else {
    echo 'failed';
}
?>