To view the terms under which this email is distributed, please go to http://disclaimer.leedsmet.ac.uk/email.htm On 07 December 2004 12:50, Rory McKinley wrote: [....] > Page_3.php starts, unserializes $_SESSION['policeman'], and begins a > lengthy SQL query that will take a few minutes to complete. > > The user wants to do something else so he\she opens a new window for > page_9.php (at this point page_3.php has yet to complete). > > Now, the question is, what will PHP do when it starts with > page_9? Will > it unserialize $_SESSION['policeman'] again, even though it > already has > an unserialized instance of $_SESSION['policeman']? If it does > unserialize, does that mean that it creates a second instance of > $_SESSION['policeman'], thereby breaking the common link that I am > trying to provide? Basically, this is a "that's not how it works" answer. The fundamental point you have to realise is that every php page is completely independent, and nothing you can do in one can directly affect anything in another (even if they use the same script to generate their output). The ways of sending information from one (invocation of a) script to another all use some external medium: POST or GET variables, a SESSION, a database, or COOKIES. Of these, only the database is purely server-side; the session very nearly is, maintaining only the session id client-side; whilst GET, POST and COOKIES all involve a full round-trip to the client. (On the client side, of course, you can use JavaScript to affect multiple windows, but that has nothing to do with server-side PHP.) So the answers to your specific questions are: yes, page_9 will unserialize again (because it knows nothing of the page_3 instance -- whatever the "it" is you're thinking of that "already has an unserialized instance", it doesn't exist); and yes, a second, completely independent, instance will be created, because there is no such common link in the way you appear to be thinking of it. Another kicker is that only one script can access the session data at any one time -- in your scenario, page_9 will stall at session_start() until page_3 releases the session lock. This will be at the end of the page_3 script, unless you explicitly release it earlier with a session_write_close(), for example. If you do this, and the page_9 script starts before the page_3 script has finished, you will have two, completely separate, local instances of $_SESSION['policeman']. Cheers! Mike --------------------------------------------------------------------- Mike Ford, Electronic Information Services Adviser, Learning Support Services, Learning & Information Services, JG125, James Graham Building, Leeds Metropolitan University, Headingley Campus, LEEDS, LS6 3QS, United Kingdom Email: m.ford@xxxxxxxxxxxxxx Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
