title: Multiple writes to a process opened with proc_open
body: <p>So I open a process with <code>$process = proc_open("my_process", $descriptors, $pipes);</code></p>
  
  <p>Then I write to the stdin of the process using <code>fwrite($pipes[0], "some_command");</code></p>
  
  <p>Then I have to close the pipe using <code>fclose($pipes[0]);</code> before i can read from the pipes stdout using <code>$output = stream_get_contents($pipes[1]);</code>. If I don't close the pipe my php script hangs on this call.</p>
  
  <p>But once I have received the output from stdout what if I want to send another command to the process...the stdin pipe is closed so I have no way to send it. So is it possible to somehow send another command to the process?</p>