参考资料：
http://www.lalit.org/lab/base62-php-convert-number-to-base-62-for-short-urls/
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<?php /** * Base62: A class to convert a number from any base between 2-62 to any other base between 2-62 * It doesn't use BC Math functions so works without the use of BC Math library. * It uses the native base_convert functions when the base is below 36 for faster execution. * The output number is backward compatible with the native base_convert function. * * Author : Lalit Patel * Website: http://www.lalit.org/lab/base62-php-convert-number-to-base-62-for-short-urls * License: Apache License 2.0 * http://www.apache.org/licenses/LICENSE-2.0 * Version: 0.1 (08 December 2011) * * Usage: * $converted_num = Base62::convert($number, $from_base, $to_base); */ class Base62 { /** * Converts a number/string from any base between 2-62 to any other base from 2-62 * @param mixed $number * @param integer $from_base * @param integer $to_base * @return $conveted_number. */ public static function convert($number, $from_base=10, $to_base=62) { if($to_base > 62 || $to_base < 2) { trigger_error("Invalid base (".he($to_base)."). Max base can be 62. Min base can be 2.", E_USER_ERROR); } //OPTIMIZATION: no need to convert 0 if("{$number}" === '0') { return 0; } //OPTIMIZATION: if to and from base are same. if($from_base == $to_base){ return $number; } //OPTIMIZATION: if base is lower than 36, use PHP internal function if($from_base <= 36 && $to_base <= 36) { // for lower base, use the default PHP function for faster results return base_convert($number, $from_base, $to_base); } // char list starts from 0-9 and then small alphabets and then capital alphabets // to make it compatible with eixisting base_convert function $charlist = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; if($from_base < $to_base) { // if converstion is from lower base to higher base // first get the number into decimal and then convert it to higher base from decimal; if($from_base != 10){ $decimal = self::convert($number, $from_base, 10); } else { $decimal = intval($number); } //get the list of valid characters $charlist = substr($charlist, 0, $to_base); if($number == 0) { return 0; } $converted = ''; while($number > 0) { $converted = $charlist{($number % $to_base)} . $converted; $number = floor($number / $to_base); } return $converted; } else { // if conversion is from higher base to lower base; // first convert it into decimal and the convert it to lower base with help of same function. $number = "{$number}"; $length = strlen($number); $decimal = 0; $i = 0; while($length > 0) { $char = $number{$length-1}; $pos = strpos($charlist, $char); if($pos === false){ trigger_error("Invalid character in the input number: ".($char), E_USER_ERROR); } $decimal += $pos * pow($from_base, $i); $length --; $i++; } return self::convert($decimal, 10, $to_base); } } } |