Rust nightly build detects that the access in https://github.com/davidcole1340/ext-php-rs/blob/0d9496b76cce8914469b60f90983283c2fdb0db0/src/zend/globals.rs#L287 results in a out of bounds.
Looking at the C code it seems that TRACK_VARS_REQUEST is not referenced anywhere.
Maybe someone with more knowledge about php internals can point towards where to find the $_REQUEST super global.