<?php
define('ROOT', 'path/to/your/web/folder');
$language_files = array(
	'administrator/language/en-GB/en-GB.com_rdsubs.ini',
	'administrator/language/en-GB/en-GB.com_rdsubs.sys.ini',
	'language/en-GB/en-GB.com_rdsubs.ini',
	'language/en-GB/en-GB.com_rdsubs.sys.ini',
);
$file_folders = array(
	'administrator/components/com_rdsubs',
	'components/com_rdsubs',
);
/* ====================================*/

require_once '../functions.php';

$unused_keys = getLanguageUnusedKeys($file_folders, $language_files);
echo "<pre>\n";
print_r($unused_keys);
echo "\n</pre>";

function getLanguageKeys($files)
{
	$language_keys = array();

	foreach ($files as $file)
	{
		if ((strpos($file, '.ini') === false))
		{
			continue;
		}

		$contents = file_get_contents(ROOT . '/' . $file);

		$contents = preg_replace('#^.*?([A-Z][A-Z_]+=)#s', '\1', $contents);

		$lines = explode("\n", $contents);

		$keys = array();

		foreach ($lines as $line)
		{
			if (!$line || (strpos($line, '=') === false))
			{
				continue;
			}

			$line = explode('=', $line, 2);

			$keys[$line['0']] = $line['1'];
		}

		if (empty($keys))
		{
			continue;
		}

		ksort($keys);

		$language_keys[$file] = $keys;
	}

	return $language_keys;
}

function getLanguageUnusedKeys($file_folders, $language_files)
{
	$language_keys = getLanguageKeys($language_files);

	foreach ($file_folders as $folder)
	{
		if (empty($language_keys))
		{
			break;
		}

		if (!is_dir(ROOT . '/' .$folder))
		{
			continue;
		}

		$files = listdir(ROOT . '/' . $folder);
		sort($files, SORT_LOCALE_STRING);

		foreach ($files as $file)
		{
			if (empty($language_keys))
			{
				break;
			}

			if ((strpos($file, '.php') === false) && (strpos($file, '.xml') === false))
			{
				continue;
			}

			removeUsedKeys($file, $language_keys);
		}
	}

	return $language_keys;
}

function removeUsedKeys($file, &$language_keys)
{
	$contents = file_get_contents($file);

	foreach ($language_keys as $path => $keys)
	{
		foreach ($keys as $key => $value)
		{
			if (!preg_match('#[^A-Z0-9]' . $key . '[^A-Z0-9]#s', $contents))
			{
				continue;
			}

			unset($language_keys[$path][$key]);
		}

		if (empty($language_keys[$path]))
		{
			unset($language_keys[$path]);
		}
	}
}