配列を50音の行毎に要素をまとめる

<?php
	$iro = array('おれんじ','あか','きいろ','みどり','きみどり','くろ','しろ','ぴんく','びりじあん');
  
  $kana = array(
    "あ行" => "[あ-お]",
    "か行" => "[か-こが-ご]",
    "さ行" => "[さ-そざ-ぞ]",
    "た行" => "[た-とだ-ど]",
    "な行" => "[な-の]",
    "は行" => "[は-ほば-ぼぱ-ぽ]",
    "ま行" => "[ま-も]",
    "や行" => "[や-よ]",
    "ら行" => "[ら-ろ]",
    "わ行" => "[わ-ん]",
    "その他" => ".*"
  );
  
  $result = array();
  foreach ($iro as $value) {
  
    $match = false;
    foreach ($kana as $index => $pattern) {
    if (preg_match("/^" . $pattern . "/u", $value)) {
      $result[$index][] = $value;
      
      $match = true;
        break;
      }
    }
  }
  
  print_r($result);
?>

参考サイト

教えて！goo

読み（あ行～わ行）ごとに分ける方法

http://oshiete.goo.ne.jp/qa/6669999.html