src/StringHelper.php
public static function unicode_to_utf16($str)
	{
		if (\extension_loaded('mbstring'))
		{
			return preg_replace_callback(
				'/\\\\u([0-9a-fA-F]{4})/',
				function ($match)
				{
					return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UTF-16BE');
				},
				$str
			);
		}

		return $str;
	}
public static function unicode_to_utf16($str)
	{
		if (\extension_loaded('mbstring'))
		{
			return preg_replace_callback(
				'/\\\\u([0-9a-fA-F]{4})/',
				function ($match)
				{
					return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UTF-16BE');
				},
				$str
			);
		}

		return $str;
	}
Converts Unicode sequences to UTF-16 string.

@param   string  $str  Unicode string to convert

@return  string  UTF-16 string

@since   1.3.0