CODEWITHSUNDEEP
phpsession
Young
Young

Reputation: 8356

Why session_start is needed when using session?

Why I can use setcookie without any preparation while need a session_start() before using $_SESSION?And I think works they do are similar.

Upvotes: 6

Views: 2352

Answers (4)

name
name

Reputation: 1

The session data is not necessarily stored in a file as Gordon says. With session_set_save_handler() you can define your own back end that should store the values, e.g. in a database.

All this data retrieving is handled with session_start(). This way you can easily change you back end without breaking your application.

Note: This is only one reason for session_start(), and again it does lot more then just setting cookies.

Upvotes: 0

Gordon
Gordon

Reputation: 316969

Because setcookie() defines a cookie to be sent along with the rest of the HTTP headers. That's a completely different thing than what session_start() does, e.g. creating a session or resuming the current one based on a session identifier passed via a GET or POST request, or passed via a cookie.

The first just adds something to the header and sends it to the browser, while the other gets the Session ID from $_COOKIEs or $_GET or $_POST and then tries finding the session file in the session_save_path and when found unserializing the values of it into $_SESSION and if not, create a new session, probably using setcookie in the process to set the Session Id.

See the chapter on Sessions in the PHP Manual.

**Edit** Like @Felix correctly points out below, the session is not necessarily saved in a file. It's not that important though, because the argument stays the same: `session_start` will find and (re-) initialize your session data, while `setcookie` just does what the name implies.

Upvotes: 12

Felix Kling
Felix Kling

Reputation: 816334

The session data is not necessarily stored in a file as Gordon says. With session_set_save_handler() you can define your own backend that should store the values, e.g. in a database.

All this data retrieving is handled with session_start(). This way you can easily change you backend without breaking your application.

Note: This is only one reason for session_start(), and again it does lot more then just setting cookies.

Upvotes: 1

enricog
enricog

Reputation: 4273

For explanation see the reply before mine. If you just don't want to call the start_session() function have a look at this setting in the php.ini: session.auto_start

Upvotes: 1

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