Sets the value of the given configuration option. Returns the old value on success, FALSE on failure. The configuration option will keep this new value during the script's execution, and will be restored at the script's ending.

蛁 It is currently impossible to register resource variables in a session. For example, you cannot create a connection to a database and store the connection id as a session variable and expect the connection to still be valid the next time the session is restored. PHP functions that return a resource are identified by having a return type of resource in their function definition. A list of functions that return resources are available in the resource types appendix.