Flexihash is a small PHP library which implements [http://en.wikipedia.org/wiki/Consistent_hashing consistent hashing], which is most useful in distributed caching. It requires PHP5 and uses [http://simpletest.org/ SimpleTest] for unit testing.
<?php
$hash = new Flexihash();
// bulk add
$hash->addTargets(array('cache-1', 'cache-2', 'cache-3'));
// simple lookup
$hash->lookup('object-a'); // "cache-1"
$hash->lookup('object-b'); // "cache-2"
// add and remove
$hash
->addTarget('cache-4')
->removeTarget('cache-1');
// lookup with next-best fallback (for redundant writes)
$hash->lookupList('object', 2); // ["cache-2", "cache-4"]
// remove cache-2, expect object to hash to cache-4
$hash->removeTarget('cache-2');
$hash->lookup('object'); // "cache-4"