AD to RegnalYear 西暦から元号に変換（元号新規追加されてもデータセットをコンテナ注入すればいい版）

ADtoRegnalYear.php

<?php
/**
 * 西暦から元号に変換（元号新規追加されてもデータセットをコンテナ注入すればいい版）
 *
 * @see http://tohokuaiki.hateblo.jp/entry/20110314/1300090600
 * @see https://github.com/mattn/go-era_jp
 */
declare(strict_types=1);

class YearValue
{
    private $gengo;
    private $year;
    private $toStringFormatter;

    public function __construct(string $gengo, int $year, callable $toStringFormatter = null)
    {
        $this->gengo = $gengo;
        $this->year = $year;
        $this->toStringFormatter = ($toStringFormatter) ? : function ($gengo, $year) {
            return ($year === 1) ? "{$gengo}元年" : "{$gengo}{$year}年";
        };
    }

    public function __toString()
    {
        $formatter = $this->toStringFormatter;
        return $formatter($this->gengo, $this->year);
    }
}

class ADtoRegnalYear
{
    private $yearSet;

    private $regnalYearFirst = 645;

    private $formatter = null;

    public function __construct(array $yearSet, $formatter = null)
    {
        $this->yearSet = $yearSet;
        $this->formatter = $formatter;
    }

    public function convert(int $year) : YearValue
    {
        if ($year < $this->regnalYearFirst) return false;

        foreach ($this->yearSet as $gengo => $years) {
            if ($years['start'] <= $year && $year < $years['end']) {
                return new YearValue($gengo, $year - $years['start'] + 1, $this->formatter);
            }
        }
    }
}


// $container->setFactory(ADtoRegnalYear::class, function ($container) {
//      return new ADtoRegnalYear(require_once $container->get('Config')['regnal_years']);
// })

$regnalYearConverter = new ADtoRegnalYear([
    '昭和' => ['start' => 1926, 'end' => 1989],
    '平成' => ['start' => 1989, 'end' => 9999]
]);

echo $regnalYearConverter->convert(1989);