PHP exec - 在进行过程中逐行回显输出

Question

I'm trying to find a way in which I can echo out the output of an exec call, and then flush that to the screen while the process is running. I have written a simple PHP script which accepts a file upload and then converts the file if it is not the appropriate file type using FFMPEG. I am doing this on a windows machine. Currently my command looks like so:

$cmd = "ffmpeg.exe -i ..\..\uploads\\".$filename." ..\..\uploads\\".$filename.".m4v 2>&1";
exec( $cmd, $output);

I need something like this:

while( $output ) {
    print_r( $output);
    ob_flush();  flush();  
}  

I've read about using ob_flush() and flush() to clear the output buffer, but I only get output once the process has completed. The command works perfectly, It just doesn't update the Page while converting. I'd like to have some output so the person knows what's going on.

I've set the time out

set_time_limit( 10 * 60 ); //5 minute time out

and would be very greatful if someone could put me in the right direction. I've looked at a number of solutions which come close one Stackoverflow, but none seem to have worked.

Answer 1

exec() is blocking call, and will NOT return control to PHP until the external program has terminated. That means you cannot do anything to dump the output on a line-by-line basis because PHP is suspended while the external app is running.

For what you want, you need to use proc_open, which returns a filehandle you can read from in a loop. e.g.

$fh = proc_open('.....');
while($line = fgets($fh)) {
    print($line);
    flush();
}