attachLatest.php file is a maintenance script that is quick hackjob to fix damaged imports on wikisource page records have page_latest column wrong. The program is looking for pages with column page_latest from the table page set to 0. For these pages, it then attaches the latest revision of that page according to the revision timestamp. The script finally prints out the number of pages, which have been or would be changed.
attachLatest.php does not check, if the revision, which is set as page_latest actually exists. If the page_latest field points to a non-existing revision, attachLatest.php, unless used with the --regenerate-all parameter, will not fix this.