Rename 'kohana' to 'system' to conform to the Kohana filesystem layout. I'm comfortable with us not clearly drawing the distinction about the fact that it's Kohana.

system/core/utf8/from_unicode.php

@@ -0,0 +1,68 @@
+<?php defined('SYSPATH') OR die('No direct access allowed.');
+/**
+ * utf8::from_unicode
+ *
+ * @package    Core
+ * @author     Kohana Team
+ * @copyright  (c) 2007 Kohana Team
+ * @copyright  (c) 2005 Harry Fuecks
+ * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt
+ */
+function _from_unicode($arr)
+{
+	ob_start();
+
+	$keys = array_keys($arr);
+
+	foreach ($keys as $k)
+	{
+		// ASCII range (including control chars)
+		if (($arr[$k] >= 0) AND ($arr[$k] <= 0x007f))
+		{
+			echo chr($arr[$k]);
+		}
+		// 2 byte sequence
+		elseif ($arr[$k] <= 0x07ff)
+		{
+			echo chr(0xc0 | ($arr[$k] >> 6));
+			echo chr(0x80 | ($arr[$k] & 0x003f));
+		}
+		// Byte order mark (skip)
+		elseif ($arr[$k] == 0xFEFF)
+		{
+			// nop -- zap the BOM
+		}
+		// Test for illegal surrogates
+		elseif ($arr[$k] >= 0xD800 AND $arr[$k] <= 0xDFFF)
+		{
+			// Found a surrogate
+			trigger_error('utf8::from_unicode: Illegal surrogate at index: '.$k.', value: '.$arr[$k], E_USER_WARNING);
+			return FALSE;
+		}
+		// 3 byte sequence
+		elseif ($arr[$k] <= 0xffff)
+		{
+			echo chr(0xe0 | ($arr[$k] >> 12));
+			echo chr(0x80 | (($arr[$k] >> 6) & 0x003f));
+			echo chr(0x80 | ($arr[$k] & 0x003f));
+		}
+		// 4 byte sequence
+		elseif ($arr[$k] <= 0x10ffff)
+		{
+			echo chr(0xf0 | ($arr[$k] >> 18));
+			echo chr(0x80 | (($arr[$k] >> 12) & 0x3f));
+			echo chr(0x80 | (($arr[$k] >> 6) & 0x3f));
+			echo chr(0x80 | ($arr[$k] & 0x3f));
+		}
+		// Out of range
+		else
+		{
+			trigger_error('utf8::from_unicode: Codepoint out of Unicode range at index: '.$k.', value: '.$arr[$k], E_USER_WARNING);
+			return FALSE;
+		}
+	}
+
+	$result = ob_get_contents();
+	ob_end_clean();
+	return $result;
+}