- substr: documentation ( source)
- strrpos: documentation ( source)
<?php
$snapshotUrl = 'dir1/dir2/dir3/dir4/filename.fileextension';
echo strrpos($snapshotUrl, '/');
echo PHP_EOL;
//echo substr($file = substr($snapshotUrl, strrpos($snapshotUrl, '/', '-1') + 1), 0, strpos($file, '.'));
echo substr($snapshotUrl, 0, strrpos($snapshotUrl, '/') + 1);