Run process with realtime output in PHP

Question

Hi,

I am trying to run a process on a web page that will return its output in realtime. For example if I run 'ping' process it should update my page every time it returns a new line (right now, when I use exec(command, output) I am forced to use -c option and wait until process finishes to see the output on my web page). Is it possible to do this in php?

I am also wondering what is a correct way to kill this kind of process when someone is leaving the page. In case of 'ping' process I am still able to see the process running in the system monitor (what makes sense).

Answer 1

See this:

Is there a way to have PHP print the data to a web browser in real time?

Answer 2

This should also work just fine, no need for ob_start():

for ($i = 1; $i <= 5; $i++)
{
    echo $i . ' ';
    sleep($i);
    flush();
}

Answer 3

If you're looking to run system commands via PHP look into, the exec documentation.

I wouldn't recommend doing this on a high traffic site though, forking a process for each request is quite a hefty process. Some programs provide the option of writing their process id to a file such that you could check for, and terminate the process at will, but for commands like ping, I'm not sure that's possible, check the man pages.

You may be better served by simply opening a socket on the port you expect to be listening (IE: port 80 for HTTP) on the remote host, that way you know everything is going well in userland, as well as on the network.

If you're attempting to output binary data look into php's header function, and ensure you set the proper content-type, and content-disposition. Review the documentation, for more information on using/disabling the output buffer.

Answer 4

First check whether flush() works for you. If it does, good, if it doesn't it probably means the web server is buffering for some reason, for example mod_gzip is enabled.

For something like ping, the easiest technique is to loop within PHP, running "ping -c 1" multiple times, and calling flush() after each output. Assuming PHP is configured to abort when the HTTP connection is closed by the user (which is usually the default, or you can call ignore_user_abort(false) to make sure), then you don't need to worry about run-away ping processes either.

If it's really necessary that you only run the child process once and display its output continuously, that may be more difficult -- you'd probably have to run it in the background, redirect output to a stream, and then have PHP echo that stream back to the user, interspersed with regular flush() calls.

Answer 5

Try changing the php.ini file set "output_buffering = Off". You should be able to get the real time output on the page Use system command instead of exec.. system command will flush the output