途中

nyanpasu.php

<?php
class Renge {
    public function __construct($params = ['seed' => NULL, 'delimiter' => NULL]) {
        $this->seed = $params['seed'];
        $this->delimiter = $params['delimiter'];
    }

    public function encode($string) {
        $table = $this->convert_table(['for' => 'encode']);
        foreach ($this->unpack_U($string) as $char) {
            $char = base_convert($char, 10, sizeof($table));
            $char = strtr($char, $table);
            $return_value[] = $char;
        }
        return join($this->delimiter, $return_value);
    }

    private function mb_ord($char) {
        return unpack('N', mb_convert_encoding($char, 'UCS-4BE', 'UTF-8'))[1];
    }

    private function chars($string) {
        return preg_split('//u', $string, -1, PREG_SPLIT_NO_EMPTY);
    }

    private function unpack_U($string) {
        $chars = $this->chars($string);
        foreach ($chars as &$char) {
            $char = $this->mb_ord($char);
        }
        unset($char);
        return $chars;
    }

    private function convert_table($params = ['for' => NULL]) {
        $table = array_merge(range(0, 9), range('a', 'z'));
        foreach (array_map(NULL, $table, $this->chars($this->seed)) as $key => $value) {
            if ($value[1] != NULL) $return_table[$value[0]] = $value[1];
        }
        switch ($params['for']) {
        case 'encode':
            return $return_table;
        case 'decode':
            return array_flip($return_table);
        }
    }
}

$renge = new Renge([
    'seed' => 'おうどん',
    'delimiter' => 'ひげ'
]);
echo $renge->encode('にゃんぱす');