[RESOLVED] Printing output as the script executes

Bonesnap

I'm not sure exactly how to describe this or what it's called.

Typically when a PHP script runs, if there's any output it's all displayed when the script finishes. I have seen a number of times scripts that output text as the script is executing, before it finishes. I was wondering what that is called and how to do it. At first I thought the page was doing some AJAX calls but Firebug shot down that idea fairly swiftly, so there must be a way to do it in PHP (or there's some other client-side voodoo going on that I haven't noticed).

A quick example of what I mean in case there's any confusion:

Say for instance you had a script that set up a database. Chances are there are a number of create table queries and many inserts. As the script runs, it would output to the screen that each table was successfully created and added to the database, as well as any default data. Normally when the script finished running you'd be presented with a plethora of output messages, but I would like each success message (or error) to output immediately after each table creation and insert, so you could watch in real-time (more or less) the status of the queries.

Note: the above is not what I am actually trying to accomplish. It's just an example of what (I think) I have seen.

Thanks for any insight!

Weedpacket

Perhaps you're referring to [man]flush[/man]? Oh, and turning off whatever output buffering you have set up.

Derokorian

Remember setting output_buffering Off (or zero) in php.ini MIGHT not be enough. You web server may also have output buffering enabled. I've seen this issue many times where its turned off in PHP but not in Apache and people get their entire content as once, even with [man]sleep[/man]s in the script.

bradgrafelman

And even then, don't forget about client-side buffering (e.g. the internal buffers in IE and Safari mentioned on the PHP manual page for [man]flush/man).

EDIT: Just so it's clear, note that I personally wouldn't do this. Instead, I'd use AJAX to periodically query a PHP script that can check on the progress and report back on it.

sneakyimp

bradgrafelman;11023693 wrote:
EDIT: Just so it's clear, note that I personally wouldn't do this. Instead, I'd use AJAX to periodically query a PHP script that can check on the progress and report back on it.

Some years back I recall a PHP upload progress bar that functioned by sniffing at a file in the raw post data. If you do end up setting up an AJAX script to check on the progress of a complex action, you should probably set up your script so that it can 'fork off' the lengthy operation such that you don't have to worry about execution timing out. I can imagine this being accomplished one of a few different ways:
1) access the time-consuming script in an iframe (ew!)
2) access the time-consuming script via AJAX (better, but still vulnerable to timeouts)
3) execute the script in the background via command line. I recall asking about this sort of thing before. I don't know off-hand if the long-running script is susceptible to termination when being launched this way. I'm not 100% sure, but I think I've seen certain background-launched processes get killed when one logs out of a terminal.

4) Use PHP's [man]pcntl_fork[/man] functions to fork off another process.

The other half of the puzzle is that the forked-off process would need to write data somewhere (either file or database) such that the other script (which you request repeatedly via AJAX) can be apprised of the long operation's progress.

Bonesnap

Thanks for the replies, guys. I played around with it for about an hour including tweaking the php.ini file (it's my own server) but couldn't get it to work. If I really want to do this I'll use AJAX in some way.

Weedpacket

Well, if you want to get high-tech, there are server-sent events, where "high-tech" means "not supported by Internet Explorer" (but there is mention there about a jQuery plugin that allows emulating it), or web sockets.