Maximum length of prefix in session_create_id

[jorgsowa]

Maximum length of prefix is 256 characters.

Reference:
https://github.com/php/php-src/blob/master/ext/session/session.c#L379
https://github.com/php/php-src/blob/master/ext/session/session.c#L75

[cmb69]

Maximum length of prefix is 256 characters.

Right. Thanks for the PR!

Unfortunately, the code is not clear that it is about the prefix here (and elsewhere about the length of the actual SID without prefix), but we can't easily change this, because php_session_valid_key() is public.

And the error message can be confusing:

var_dump(session_create_id(str_repeat("a", 257)));

Warning: session_create_id(): Prefix cannot contain special characters. Only aphanumeric, ',', '-' are allowed in …
bool(false)

[jorgsowa]

Thank you. I created related PR for php-src also: php/php-src#15338