Okay. The scenario is that you have Sphider in stalled into a directory name "sphider". In you settings, English is set as the language, so when 'sphider/search.php' is used, the language is English.
Now you want to also present a search option in Spanish. Create a directory named 'es_search'. The name doesn't matter, this is just an example. Now copy 'sphider/search.php' to 'es_search/search.php'.
In the 'es_search' directory, edit search.php. Lines 61-67 show:
$include_dir = "./include";
$template_dir = "./templates";
$common_template_dir = "./common_template";
$settings_dir = "./settings";
$language_dir = "./languages";
$calendar_dir = "./calendar";
Change the paths so that they read:
$include_dir = "../sphider/include";
$template_dir = "../sphider/templates";
$common_template_dir = "../sphider/common_template";
$settings_dir = "../sphider/settings";
$language_dir = "../sphider/languages";
$calendar_dir = "../sphider/calendar";
Now we need to add a line in three different places. (Actually. since I am betting you only want to use the classic search option and are not interested in RSS or image searches, only the first is critical, but do all three JUST IN CASE you use the others in the future and forgot what you did!)
Lines 199, 284, and 333 each read:
After each of these lines, add:
$language = 'es';
The end result in all three places will be:
$language = 'es';
What you have done is load the configuration settings, then you have OVERRIDDEN the language setting. If you want a third language, say German. create another directory 'de_search', copy search.php there, and make the same changes except it will be "$language = 'de';" instead.
[You may have noticed line 79 - require $settings_dir."/conf.php";. Don't worry about that one. That instance is only looking for which template to use and has nothing to do with language.]