Paul Reinheimer has a suggestion on how to improve the PHP manual to be an even better resource - enhancing the "see also".
Something I'd like to see in PHP is a little more in the See Also section. They're pretty good, but it's not quite as spider-web like as I'd like. For example, yesterday I added a few links from md5() and sha1() to hash(). Lot of people know about md5() and sha1() within PHP, but I find hash() is rather unknown overall, which is a pity as it exposes a tone of different hashing algorithms.
You can see an example of his updates in the md5 manual page linking it to sha1_file, crc32, sha1 and the hash functions.