Multi-Context System Documentation

The Multi-Context System allows a single ABCD OPAC installation to serve multiple libraries, institutions, or database collections independently. By using a simple URL parameter (?ctx=...), the system switches the physical directory where it looks for databases (bases), effectively creating separate environments.

1. How it Works

Instead of having a hardcoded path to the databases (e.g., /var/www/bases/), the system uses a Mapping Logic:

1. The User Request: The user accesses a URL like http://myserver/opac/?ctx=law.
2. The Lookup: The system checks the config_opac.php file for a "map" that links the alias law to a specific physical folder on the server (e.g., C:/abcd/bases-law/).
3. The Switch: If the context is valid, the system sets the internal $db_path variable to that specific folder. All subsequent operations (searching, displaying records, loading configuration files) will happen inside that folder.
4. Session Persistence: The system remembers the current context in the user's session. This ensures that if the user clicks a link that accidentally omits the ?ctx= parameter, they remain in the correct library.

2. How to Enable It

To enable this feature, you must edit the config_opac.php file located in the opac/ directory (or the central configuration directory, depending on your setup).

Step 1: Activate the Feature Locate the $opac_multi_context variable and set it to true.

$opac_multi_context = true;

Step 2: Configure Strict Mode (Optional but Recommended) Strict mode prevents users from accessing the OPAC without specifying a context (which would otherwise load the default/root databases).

$opac_strict_mode = true; // Blocks access if ?ctx= is missing

Step 3: Define the Context Map This is the most important step. You define an array where the key is the URL alias and the value is the full physical path to the bases folder for that client.

$opac_context_map = array(
    // 'URL_ALIAS'  =>  'PHYSICAL_PATH_ON_SERVER'
    'demo'          =>  'C:/xampp/htdocs/ABCD2/www/bases-examples_Windows/',
    'medicine'      =>  'C:/xampp/htdocs/ABCD2/www/bases-medicina/',
    'law_library'   =>  '/var/www/abcd/bases-law/',
);

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⚙️ Important Points of config_opac.php

The config_opac.php file is the brain of the OPAC. It is structured into logical blocks to separate user configuration from system logic.

Block 1: Initialization

This section handles PHP settings and loads the core ABCD configurations.

• Session Start: It ensures a PHP session is active to store the user's current context and language.
• Central Config: It includes central/config.php to get system-wide defaults.

Block 2: User Configuration (Edit Here)

This is where administrators make changes.

• Multi-Context Switches: As explained above ($opac_multi_context, $opac_strict_mode).
• Context Map: The list of available libraries ($opac_context_map).

Block 3: Context Resolution Logic

This section contains the logic that determines which database path ($db_path) to use. You generally do not need to edit this.

• URL Detection: Checks if $_REQUEST['ctx'] exists and matches an entry in the map.
• Session Fallback: If the URL has no context, it checks $_SESSION to see if the user was already browsing a specific library.
• Security Check: If Strict Mode is on and no context is found, it kills the process with an "Access Denied" message (unless running in the Administrative module).
• Sanitization: Ensures paths end with a correct directory separator (/).

Block 4: Mode Logic (Integrated vs. Single Base)

Controls the search behavior:

• Integrated Mode: Searches across all databases defined in bases.dat. Active by default on the home page.
• Single Base Mode: If the URL contains &base=marc, this logic automatically disables Integrated Mode so the search is restricted to that specific database.

Block 5: Language Detection

A robust logic to determine the interface language, prioritized as follows:

1. Session (Admin): If an administrator is logged in, their language preference wins.
2. URL Request: If the user clicks a flag (?lang=pt), that choice takes precedence and is saved.
3. Session (Visitor): Remembers the visitor's choice during navigation.
4. Browser: Tries to detect the browser's default language.
5. Default: Falls back to the system default.

Block 6: Visual and Functional Settings

Loads specific visual settings for the active base.

• opac.def: Reads the specific configuration file for the current language/base (colors, texts).
• $restricted_opac: Defines if the OPAC requires login (Y or N).
• Global Styles: Checks for global_style.def to apply custom CSS overrides per context.