在PHP中维护浏览器选项卡之间的状态

Question

I'm building a web application that allows users to run a query against one of two databases. They are only allowed to submit 1 query to each database at a time. Currently, I'm setting $_SESSION['runningAdvancedQuery'] (for instance) to let me know if they're running a query. This is to prevent someone from opening up a 2nd browser tab and hitting the resource again. It works great except...

If I start a query in a tab, then close that tab before it finishes, the flag does not get unset. Therefore, if I reopen the page, I cannot run any queries because it thinks I have one still running. Anyone have advice for getting around this?

Answer 1

Set this value not to for example 1, but to unix timestamp, and do checking by comprasion last-query-timestamp to now, setting up some time difference that must go by to execute next query. Remeber to set a block-time to safe value - longest time which query can be executed. If user closes his tab, after a short time he will be "unlocked".