[ticket/10848] Redirect from adm to installer correctly.

PHPBB3-10848

phpBB/includes/functions.php

@@ -1176,6 +1176,36 @@ else
 	}
 }
 
+/**
+* Eliminates useless . and .. components from specified path.
+*
+* @param string $path Path to clean
+* @return string Cleaned path
+*/
+function clean_path($path)
+{
+	$exploded = explode('/', $path);
+	$filtered = array();
+	foreach ($exploded as $part)
+	{
+		if ($part === '.' && !empty($filtered))
+		{
+			continue;
+		}
+
+		if ($part === '..' && !empty($filtered) && $filtered[sizeof($filtered) - 1] !== '..')
+		{
+			array_pop($filtered);
+		}
+		else
+		{
+			$filtered[] = $part;
+		}
+	}
+	$path = implode('/', $filtered);
+	return $path;
+}
+
 if (!function_exists('htmlspecialchars_decode'))
 {
 	/**