This constant allows the use of plugins that have not yet been declared compatible with the version of SPIP used. This allows them to be tested, used or debugged if necessary.
For example, when SPIP 4.0 is released, it can be defined as such in the mes_options.php file, in order to be able to use plugins that are not declared compatible with SPIP 4.0 but are declared compatible with SPIP 3.2.
define('_DEV_VERSION_SPIP_COMPAT', '3.2.0');
Rq: when you change this constant, it immediately becomes possible to activate plugins already installed, but the local cache of plugin repositories is not updated with the new possibilities, and the search among plugins cannot provide the plug-ins that the new compatibility constant has made accessible. So you have to delete the declared repositories [1], and then reinstall them, so that the search returns the full set of results now possible.
See also other constants:
- constant _COMPORTEMENT_HISTORIQUE_IMG_DOC_EMB
- constant _COMPORTEMENT_HISTORIQUE_PORTFOLIO