Development:Developer FAQ

Revision as of 07:39, 12 May 2008 by Valery Fremaux (talk | contribs) (How do I insert/retrieve records in the database, without creating my own database connections?)

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Template:FAQ

Help for new coders

Where can "newbies" to Moodle get help?

The General developer forum! Feel free to ask any question, no matter how basic or advanced. Many people ask different levels of question every day, and the community is generally welcoming and quick to respond.

Moodle's database

Where can I see a schema for the structure of the Moodle database?

When installing Moodle, the database tables are generated and updated by various db-handling scripts located in various places. There is no canonical schema representation, although the coding guidelines for database structure give an outline of the general approach.

The reason that the database information isn't stored in one place is because of Moodle's modular structure. Each activity module, for example, comes as a folder with script files inside. If the module needs to store information in the database, it must include scripts in a "db" subfolder which define and update the database structure.

How to get/set information when writing new Moodle code

How do I find out the currently-logged-on user?

The global object $USER, which contains the numeric $USER->id among other things.

How do I find out the current course?

The global object $COURSE, which contains the numeric $COURSE->id

How do I insert/retrieve records in the database, without creating my own database connections?

Always use the "datalib" functions, such as insert_record() or get_record(). Since Moodle 1.7 these are found in lib/dmllib.php. Using these functions helps with database abstraction (e.g. running on either MySQL or Postgres) as well as maintaining a single database connection. Moodle uses ADODB for database abstraction.

Look at the documentation for datalib.php - Broken Link for the list of functions and details of use.

How do I get/set configuration settings?

To get config values you would typically access the global $CFG object directly, which is automatically created by the core Moodle scripts. To set these "main" config values use set_config($name, $value). The values are stored in the Moodle "config" database table, but these functions take care of cacheing on your behalf, so you should always use these rather than fetching the records directly.

There is also a second table of config settings specifically for plugins ("config_plugin"). These are not automatically loaded into the $CFG object, so to fetch these you would use get_config($plugin, $name). To set them use set_config($name, $value, $plugin).

See also