<?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);
}
}
}
