The searching is based on the specified language code. In particular,
a file with the same name will be looked for under the subdirectory
whose name is the same as the language code. For example, given the file "path/to/view.php"
and language code "zh-CN", the localized file will be looked for as
"path/to/zh-CN/view.php". If the file is not found, it will try a fallback with just a language code that is
"zh" i.e. "path/to/zh/view.php". If it is not found as well the original file will be returned.
If the target and the source language codes are the same,
the original file will be returned.