note 108304 added to function.mt-rand

to complete the very good idea from thegreatall at gmail dot com : Because i didn't understand at all the idea behind the use of hex to generate randoms, and worst the use of these specific numbers (0x1D39D3E06400000 and 0x41C21CB8E0FFFFFF), here is an explanation on why this method still is the BEST and QUICKEST way to get alphanumerics randoms. The following example function generates a pure random, exact 6 characters alphanumeric, on 32bit or more OS: <? function random36($length = 6) { // 6 characters $result = substr(base_convert(mt_rand(60466176, 2147483647), 10, 36), 0, $length); // for 12 characters or more, simply duplicate the stuff $result = substr(base_convert(mt_rand(60466176, 2147483647), 10, 36).base_convert(mt_rand(60466176, 2147483647), 10, 36), 0, $length); } ?> Randoms are between 100000 and zik0zj = 2087017471 possibilities The reason we choose a random between 60466176 and 2147483647 exactly is based on the platform limitation : 1) mt_getrandmax() 32bits : mt_getrandmax(); //2147483648 64bits : mt_getrandmax(); //18446744073709551616 2) mt_rand(in, between) mt_rand(in, 2147483648) returns an error ! The maximum can only be 2147483647 : random from 0 to 2147483647 = 2147483648 possibilities :-) 3) maximum base_convert(integer, 10, 36) This convert a base 10 integer (0-9) to an alphanumeric base 36 number (0-z). Since we want an always fixed length alphanumeric number, and depending on the OS limitations (here, 32bits), at first sight the possible base 36 randoms we can have are between : 100000 and zzzzzz But, since our maximum is 2147483647, ou base 36 maximum will be: base_convert(2147483647, 10, 36); //zik0zj 4) minimum Our base 10 minimum will be: base_convert('100000', 36, 10); //60466176 5) QUICKEST way Based on some 100000 times loop tests i made, with different functions on this page, the results are clear : Robin Leffmann : 1s (but it's binary) thegreatall at gmail dot com : 1.8s sheyd dot fr : 4.3s james at coretelecom dot co dot uk : 27s www.mrnaz.com : >30s MagicalTux at ooKoo dot org : 7.3s phil _ ozil at hotmail dot com : 4.9s ---- Server IP: 195.221.21.36 Probable Submitter: 82.244.50.105 ---- Manual Page -- http://www.php.net/manual/en/function.mt-rand.php Edit -- https://master.php.net/note/edit/108304 Del: integrated -- https://master.php.net/note/delete/108304/integrated Del: useless -- https://master.php.net/note/delete/108304/useless Del: bad code -- https://master.php.net/note/delete/108304/bad+code Del: spam -- https://master.php.net/note/delete/108304/spam Del: non-english -- https://master.php.net/note/delete/108304/non-english Del: in docs -- https://master.php.net/note/delete/108304/in+docs Del: other reasons-- https://master.php.net/note/delete/108304 Reject -- https://master.php.net/note/reject/108304 Search -- https://master.php.net/manage/user-notes.php