Unable to use PHP ini option `ffi.preload`

[gaelreyrol]

As said in the OpenTelemetry PHP documentation, fibers support can be enabled with OTEL_PHP_FIBERS_ENABLED.

Using non-CLI SAPIs (e.g. fpm, fastcgi) may require to preload some bindings like:

ffi.preload=vendor/open-telemetry/context/fiber/zend_observer_fiber.h
opcache.preload=vendor/autoload.php

But when building the composer package from PHP built with buildPhpFromComposer (using loophp/nix-shell flake), the underlying derivation composer-local-repo-plugin fails as it is unable to start FFI module because it could not find the file mentioned in the option ffi.preload.

nix log /nix/store/0jp32vgnhlr0ks6ky2z4sylmqrj0dwpw-composer-local-repo-plugin-1.0.3.drv:

@nix { "action": "setPhase", "phase": "unpackPhase" }
unpacking sources
unpacking source archive /nix/store/l5a037w0nj3iyfm8xhxh48vc6pa4m90l-source
source root is source
@nix { "action": "setPhase", "phase": "patchPhase" }
patching sources
@nix { "action": "setPhase", "phase": "updateAutotoolsGnuConfigScriptsPhase" }
updateAutotoolsGnuConfigScriptsPhase
@nix { "action": "setPhase", "phase": "configurePhase" }
configuring
@nix { "action": "setPhase", "phase": "buildPhase" }
building

Warning: FFI: failed pre-loading 'vendor/open-telemetry/opentelemetry/src/Context/fiber/zend_observer_fiber.h', file doesn't exist in Unknown >

Fatal error: Unable to start FFI module in Unknown on line 0

The PHP derivation built from buildPhpFromComposer has the option but it does not contain the file from ffi.preload.