The behaviour of these functions is affected by
settings in php.ini.
For further details and definitions of the PHP_INI_* modes, see the
configuration setting may be set.
Here’s a short explanation of the configuration
Allows enabling (“true”) or disabling
(“false”) FFI API usage, or restricting it only to the CLI
SAPI and preloaded files (“preload”).
The FFI API restrictions only affect the FFI class, but not
overloaded functions of FFI\CData objects. This means that it is possible
to create some FFI\CData objects in preloaded files, and then to
use these directly in PHP scripts.