PHP I/O console

Question

I've got an application (usual .exe file) that I can run in console (e.g. as daemon). It works fine and Input/Output is just standard STDIN/STDOUT so from the console (windows or debian) there is no problem. But I need interact with that with php (my php script).

That's again no problem because there is a lot of 'stuff' in PHP to do that (proc_open, exec, system, pipes, strings etc etc etc). The problem's that the application must work during getting/receiving data (in simple words -that's a daemon) but all the functions above waiting for the end of execution of the command and after return result.

from php.net

Note: If a program is started with this function, in order for it to continue running in the
background, the output of the program must be redirected to a file or another output
stream. Failing to do so will cause PHP to hang until the execution of the program ends.

It's known how to redirect to another input/output (eg. to file) with > | & etc.:

$last_line = system("myfile.exe>file2.txt", $retval);

that works fine even as daemon. Although I can't get how to implement an input in the mode. However, my main problem how to redirect standard output to a non-file resource. On php.net is written:

Windows compatibility: Descriptors beyond 2 (stderr) are made available to the child process as inheritable handles, but since the Windows architecture does not associate file descriptor numbers with low-level handles, the child process does not (yet) have a means of accessing those handles. Stdin, stdout and stderr work as expected.

So it woud be easy just command>&3 but I can't define new (my own) handles for I/O.

So the question is How to implement/handle input/output (to BOTH ways) for a daemon!!!

I've scrutinized tons of sources in Internet but didn't get a normal answer for PHP. It's elementary for Java, for example, for C/C++ but not for PHP.

Maybe somebody help me - I would be very appreciate!

Joffrey · Accepted Answer · 2014-08-23 18:54:32Z

The proc_* functions are more powerful than you expect. Your assumption these functions will block is not correct.

After calling proc_open you can set every pipe to non-blocking. This will result in a way you can use fread without waiting for input from the process, and try to fwrite without waiting for the process to be able to accept it.

Also I would recommend to use socket_select to make sure you do not get into a tight loop trying to read/write to your executed process. A select construction will break it's sleep period when a file pointer (pipe in your case) is ready for reading or to be written to.

$descriptorspec = array(
  0 => array("pipe", "r"), // stdin
  1 => array("pipe", "w"), // stdout
  2 => array("file", "r") // stderr );

$process = proc_open('php', $descriptorspec, $pipes);

foreach($pipes as $pipe)
  stream_set_blocking($pipe, 0);

For more information see the documentation and comments of socket_select, stream_set_blocking, and proc_open.

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