How many PHP scripts can run concurrently via http request?

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How many PHP scripts can run concurrently via http request?

Hello all,

I know PHP scripts can run concurrently, but I notice that when I run a script and then run another script after it. It waits for the first to finish and then it does what it has to do?

Is there an Apache config I have to change or do I use a different browser or something?!!

Thanks all

EDIT

If I go to a different browser, I can access the page/PHP script I need?! Is this limiting the number of requests by browser? Apache?

If you run php under fastcgi you can probably avoid this restriction.

ternaryOperator 2010-01-06 19:26:57

+2 A:

Two things comes to mind:

HTTP 1.1 has a recommend maximum limit of 2 simultaneous connections to any given domain. This would exhibit the problem where you can only open one page on a site at a time unless you switch browsers.
Edit: This is usually enforced by the client, not the server
If your site uses sessions, you'll find out that only one page will load at a time...
...unless you call session_write_close(), at which point the second page can now open the now-unlocked session file.

R. Bemrose 2010-01-06 19:39:44

Very Interesting. I didn't know those two facts. What if the second request isn't going to write any session data but use it. PHP pauses regardless is there is a session_start anywhere in the script?

Abs 2010-01-06 19:44:24

For point 1 - how can I increase this recommended limit?

Abs 2010-01-06 19:46:27

I believe session_write_close() still allows you to read session values, but I haven't tested it (we don't use PHP where I work).For point 1, you can't really... it's the client that does this. On Firefox, I believe the FasterFox plugin can do it. IE uses a registry key: http://support.microsoft.com/kb/282402

R. Bemrose 2010-01-06 19:56:39

+1 because it's probably #2. I've never known any web server actually enforce #1.

Ben James 2010-01-06 19:57:03

@Ben James: Yes, #1 is usually enforced by the client. I've added a note about that to the answer.

R. Bemrose 2010-01-06 19:58:49

@R. Bemrose - I would use that function but the thing is the first script takes quite a while to finish and has to make use of session variables throughout. So the second has to just wait. I probably have to rewrite some parts of my script.

Abs 2010-01-06 20:00:56

@R. Bemrose Would I have the same problem using a database based session? Or will the DB sort out the problem of concurrency? It should allow me to read multiple times without changing variables I guess?

Abs 2010-01-06 21:34:39

@Abs: I'm not sure. I haven't really worked with PHP's database-based sessions. I would assume a DB-based session wouldn't lock, though.

R. Bemrose 2010-01-07 14:21:42

I haven't had this problem with apache / php, the project I work on runs 3 iframes each of which is a php script + the main page, apache handles all 4 at the same time.

You may want to check your apache configuration and see how the threading is setup.

This article may help: http://www.devside.net/articles/apache-performance-tuning

Jim Ford 2010-01-06 20:02:46

ansaurus

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How many PHP scripts can run concurrently via http request?

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