TYPO3 CMS offers versioning of the database elements it manages. This versioning system allows you to work on future versions of content without affecting the live content. It is used by workflow systems to offer a process for such content, going from creation, editing to review and publishing.
Versioning is available in the core API by default, but to gain access to management tools you must install the system extensions "version" and "workspaces".
Versioning must be enabled on a per-table basis in the "ctrl" section of the TCA array for the given table. In addition a fixed set of fields has to exist for the management of versions. All of these technical details are specified in the description of the "versioningWS" TCA property. All other versioning and workspace-related properties are also described there.
Future and past versions of records in TYPO3 CMS remain in the same table as the live version. However, all "offline" versions have a pid value of "-1" to set them apart. Furthermore they have a database field called "t3ver_oid" which points to their live ("online") counterpart.
When a future/past version is swapped with the live version it is done by swapping all field values except the uid and pid fields (and of course versioning related fields are manipulated according to their function). It means that online content is always identified by the same id as before and therefore all references are kept intact.
Versioning is easy for existing elements. However, moving, creating and deleting poses other problems. This is solved the following way:
- Deleting elements is done by actually creating a new version of the
element and setting a flag in the new version (
t3ver_state = 2) that indicates the live element must be deleted upon publishing the versions.
- Creating elements is done by first creating a placeholder element
which is in fact live but carrying a flag (
t3ver_state = 1) that makes it invisible online. Then a new version of this placeholder with the flag (
t3ver_state = -1) is made which is what is modified until published.
- Moving elements is done by first creating a placeholder element which
is in fact live but carrying a flag (
t3ver_state = 3) that makes it invisible online. It also has a field, "t3ver_move_id", holding the uid of the record to move (source record). In addition, a new version of the source record is made with
t3ver_state = 4(move-to pointer). This version is necessary in order for the versioning system to have something to publish for the move operation. So in summary, two records are created for a move operation in a workspace: The placeholder (online, with
t3ver_state = 3and "t3ver_move_id" set) and a new version (
t3ver_state = 4) of the online source record (the one being moved).
- Unique fields like a page alias or user name are tricky in a versioning scenario because the publication process must perform a check if the field is unique in the "Live" situation. The implications of implementing this means that we have chosen a solution where unique fields are simply not swapped at all! It means that publication of a new version of a page cannot and will not alter the alias of the live version. The "Live" unique value will remain until changed in the live version.
- You can hide fields with the "unique" keyword when there are offline versions. This is done with the display condition:
'displayCond' => 'VERSION:IS:false',
This is an overview of how permissions are handled in relation to versioning:
- Read permissions are evaluated based on the live version of pages (as the basic rule). The read permissions of the offline page version in a workspace is not observed.
- The ID of the live record is used so the live records display- permissions get evaluated.
- To create a new version the user must have read permission to the live record he requests to version
- A new version of a page will inherit the owner user, group and permission settings from the live record
- To publish, a user must have general publishing permission in the workspace, for instance be the owner of it or have access to the Live workspace.
- In addition, the user must have read and edit access to the offline version being published plus edit access to the live version that a publishing action will substitute!
- The permissions of a new version of a page follows the page when published.
- For all editing it is required that the stage of the versioned record (or root point) allows editing.
- Page records:
- Permission to edit is always evaluated based on the pages own permission settings and not the live records.
- Records from non-pages tables:
- Always based on the live parent page.
- When new records are created with a version and live place holder the permissions depend on the live page under which the record is created.
- Records can be moved as long as the source and destination root point to a stage that allows it.
- New records created with a placeholder element can be moved freely around.
- Generally, the stage of a moved record has to allow for editing plus regular permissions for moving.
- If a record supports versioning it will be marked for deletion if all usual requirements are fulfilled at the time of the delete request: delete access to record, no subpages if recursive deletion is not enabled and no disallowed table records are found. As soon as the record is marked for deletion any change to the record and subpages that would otherwise prevent deletion for the user will not be effective. The record will be deleted upon publication!
- If you try to delete a Live record for which a version is found in the workspace, that version is deleted instead.
- Detaching versions from a workspace and raising stage of versions can be done as long as the user has edit permission to the record.