YYYYMMDDから和暦求めるようなやつ

gistfile1.aw

<?php

function toWareki ( $y, $m, $d ) {

	$data = array(
		array( 'nengou' => '明治', 'from' => 18680908, 'to' => 19120730,),
		array( 'nengou' => '大正', 'from' => 19120730, 'to' => 19261225,),
		array( 'nengou' => '昭和', 'from' => 19261225, 'to' => 19890107,),
		array( 'nengou' => '平成', 'from' => 19890107, 'to' => 99999999,),
	);

	$year = $y;
	$nengou = '';
	$ymd = (int)sprintf( '%04d%02d%02d', $y, $m, $d );

	foreach( $data as $d ) {
		if ( $d['from'] <= $ymd && $ymd < $d['to'] ) {
			$nengou = $d['nengou'];
			$year = $y - ( (int)substr( (string)$d['from'], 0, 4) - 1 );
			break;
		}
	}

	return array(
		'nengou' => $nengou,
		'year' => $year,
	);
}

print_r( toWareki(2012, 4, 30) );