What is the distribution of php's random_int function?
I guess it comes down to the distribution of getrandom(2) and /dev/urandom? How are they distributed?
Can random_int be used for a uniform distributed random number generator?
From php manual for random_int:
On Windows, CryptGenRandom() will always be used.
On Linux, the getrandom(2) syscall will be used if available.
On other platforms, /dev/urandom will be used.
Which means the distribution is OS dependant...
So, I think it's not so easy to answer to the original question 'What is the distribution of php's random_int function?'.. On Linux, for example, from a discussion about int getrandom(void *buf, size_t buflen, unsigned int flags);:
[...] The GRND_RANDOM flag bit can be used to switch to the /dev/random pool, subject to the entropy requirements of that pool [...]
So, based on different run-time arguments, random distribution may differ in the same OS...