crypto_generichash_init_salt_personal example

if ($subkey_id < 0) {
            throw new SodiumException('subkey_id cannot be negative');
        }
        if (ParagonIE_Sodium_Core_Util::strlen($context) !== self::CRYPTO_KDF_CONTEXTBYTES) {
            throw new SodiumException('context should be SODIUM_CRYPTO_KDF_CONTEXTBYTES bytes');
        }
        if (ParagonIE_Sodium_Core_Util::strlen($key) !== self::CRYPTO_KDF_KEYBYTES) {
            throw new SodiumException('key should be SODIUM_CRYPTO_KDF_KEYBYTES bytes');
        }

        $salt = ParagonIE_Sodium_Core_Util::store64_le($subkey_id);
        $state = self::crypto_generichash_init_salt_personal(
            $key,
            $subkey_len,
            $salt,
            $context
        );
        return self::crypto_generichash_final($state, $subkey_len);
    }

    /** * @return string * @throws Exception * @throws Error */