sodium_crypto_stream

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_stream — Generate a deterministic sequence of bytes from a seed

sodium_crypto_stream(int $length, string $nonce, string $key): string

Generate a deterministic sequence of bytes from a seed, using the XSalsa20 stream cipher.

length: The number of bytes to return.
nonce: A number that must be only used once, per message. 24 bytes long. This is a large enough bound to generate randomly (i.e. random_bytes()).
key: Encryption key (256-bit).

String of pseudorandom bytes.