Inserts or updates a variable with a given variable_key. All variable-types are supported.
Geeft TRUE terug bij succes, FALSE indien er een fout is opgetreden.
Warnings (E_WARNING level) will be issued if shm_identifier is not a valid SysV shared memory index or if there was not enough shared memory remaining to complete your request.
Opmerking: This function does not work on Windows systems.