Generate a random string of non-ambiguous numbers and letters.
Doing md5(microtime()) is nice but it is 32 chars long. I could use base64, but it contains weird characters like "/" and "=".
So how do I restrain the encoding to alphanumeric ? I found the inspiration from Ross Duggan and I added a random function. He also removes a couple ambiguous chars, which I think is a nice touch.
The choice of random could be discussed but the idea is there.
UPDATE: As suggested by a friend, it is simpler and a better use of the range of available entropy to generate each character separately. You can see the old version in the Gist.
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| <?php | |
| class CodeGenerator | |
| { | |
| private static $alphabet = '23456789abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'; | |
| private static $max_offset = 55; | |
| /** | |
| * Generate a random character of non-ambiguous number or letter. | |
| * @return string the character | |
| */ | |
| public static function randomChar() | |
| { | |
| $index = mt_rand(0, self::$max_offset); | |
| return self::$alphabet[$index]; | |
| } | |
| /** | |
| * Generate a random string of non-ambiguous numbers and letters. | |
| * @param $length Size of generated string | |
| * @return string | |
| * @throws InvalidArgumentException | |
| */ | |
| public static function generate($length = 16) | |
| { | |
| if ($length < 1) { | |
| throw new InvalidArgumentException(__METHOD__ . ' expects a $length argument of at least 1, input was: ' . $length); | |
| } | |
| $random = ''; | |
| for ($i=0; $i < $length; $i++) { | |
| $random .= self::randomChar(); | |
| } | |
| return $random; | |
| } | |
| } |