Enhance PHP File Localization

To understand the task - please, look http://php84.altanista.net
User - free
Passw - lance
this is the raw search interface with dummy database.
1) Enter a search word 'lorem' - you will see Categories, Levels and Weights on the left side.
2) Now on the top menu change EN language to ES language (search results will be lost) - and enter a search word 'lorem' again.

As you can see - interface is translated to ES (Spanish) - but Categories (Category One, etc) and Levels (Level First, etc) - NOT.
This functionaly provides by
SearchController.php (open and see attached) where used
protected $levelDict = array(... - for Levels
protected $categDict = array(... - for Categories

** TASK ONE
Saving same functionality I want to extend translation to Categories and Levels too - using my additional dictionaries added to SearchController.php
$levelDictLang instead of $levelDict
$categDictLang instead of $categDict

Pay attention that in the code already stated
if ($this->req->get('lang')) {
$lang = $this->req->get('lang');
} else {
$lang = 'en';
}
...means if no translation available - use English - same behaviour should be saved.
Of course such a modification should not affect or spoil the existing search functionality

** TASK TWO
When the TASK ONE solved - I'd like to move the dictionaries to external files like
en_lang
es_lang
de_lang
etc - connecting on demand -> to avoid overloading of SearchController.php by the content of ALL dictionaries.

I suppose such the tasks should not be a problem for a PHP programmer.
I will give FTP access to a test server where the script is located.
Please, apply with a bid or discuss.