large raw binary base conversion php

large raw binary base conversion php

/**
   Enables alphanumeric encoding and decoding of binary data for easy transportation over any medium
   Works using the GMP extension to avoid PHP's base_convert loss of preceision when working with large numbers e.g. a 256 bit key
   converts the binary to hex then to an arbitrary base, 62 is best in my experince
*/
class BinaryBaseChanger {
   const STORAGE_BASE = 16;

   public static function changeTo($binary_data, $base_to) {
      $hexadecimal = bin2hex($binary_data);

      return self::gmpBaseChange($hexadecimal, self::STORAGE_BASE, $base_to);
   }

   public static function changeFrom($encoded_hex, $base_from) {
      $hexadecimal = self::gmpBaseChange($encoded_hex, $base_from, self::STORAGE_BASE); 

      // if its not even it will be rejected by hex2bin
      // add a precceding zero if its uneven
      if(strlen($hexadecimal) % 2 != 0) {
         $hexadecimal = '0'.$hexadecimal;
      }
      
      return hex2bin($hexadecimal);
   }

   private static function gmpBaseChange($input, $base_from, $base_to) {
      return gmp_strval(gmp_init($input, $base_from), $base_to);
   }
}