note 107920 added to function.hash

On two different servers I found that crc32() relates to hash('crc32b',) This may be good to know if you are writing a crc32_file function based on hash_file. (The example does not compensate for negative crc32 results) <?php $val = 'hello'; var_dump(crc32($val) == ( '0x' . hash('crc32b', $val) ) ); // bool(true) var_dump(crc32($val) == ( '0x' . hash('crc32', $val) ) ); // bool(false) ?> Also if you are looking for a way to reduce collisions and still keep the hash result small (smaller than say md5) you could get a nice database friendly 64 bit value by using hash/crc32 and hash/crc32b, which is slower than a single md5 but the result may be more suitable for certain tasks. <?php $val = 'hello'; $crc64 = ( '0x' . hash('crc32', $val) . hash('crc32b', $val) ) ); var_dump($crc64); // string(18) "0x3d6531193610a686" var_dump($crc64 + 0); // int(4423996193312384646) ?> (examples tested on php 5.2.17) note: ('0x' . $hex . + 0) is faster than base_convert($hex,16,10) ---- Server IP: 66.207.199.35 Probable Submitter: 69.159.196.196 ---- Manual Page -- http://www.php.net/manual/en/function.hash.php Edit -- https://master.php.net/note/edit/107920 Del: integrated -- https://master.php.net/note/delete/107920/integrated Del: useless -- https://master.php.net/note/delete/107920/useless Del: bad code -- https://master.php.net/note/delete/107920/bad+code Del: spam -- https://master.php.net/note/delete/107920/spam Del: non-english -- https://master.php.net/note/delete/107920/non-english Del: in docs -- https://master.php.net/note/delete/107920/in+docs Del: other reasons-- https://master.php.net/note/delete/107920 Reject -- https://master.php.net/note/reject/107920 Search -- https://master.php.net/manage/user-notes.php