php exec() with timeout

exec_timeout.php

<?php
/**
 * Execute a command and return it's output. Either wait until the command exits or the timeout has expired.
 * The syntax in compatible to the inbuilt exec().
 *
 * This is an improved version (parameter and output-compatible to exec()) of the original by Erik's Code here:
 * https://blog.dubbelboer.com/2012/08/24/execute-with-timeout.html
 *
 * @param string $cmd     Command to execute.
 * @param string $output  Returns command output
 * @param string $exitcode  Returns exitcode
 * @param number $timeout Timeout in seconds (default 10s).
 * @throws \Exception
 */
function exec_timeout($cmd, &$output, &$exitcode, $timeout = 10) {
  
  // File descriptors passed to the process.
  $descriptors = array(
    0 => array('pipe', 'r'),  // stdin
    1 => array('pipe', 'w'),  // stdout
    2 => array('pipe', 'w')   // stderr
  );

  // Start the process.
  $process = proc_open('exec ' . $cmd, $descriptors, $pipes);

  if (!is_resource($process)) {
    throw new \Exception('Could not execute process');
  }

  // Set the stdout stream to non-blocking.
  stream_set_blocking($pipes[1], 0);

  // Set the stderr stream to non-blocking.
  stream_set_blocking($pipes[2], 0);

  // Turn the timeout into microseconds.
  $timeout = $timeout * 1000000;

  // Output buffer.
  $output = '';

  // While we have time to wait.
  while ($timeout > 0) {
    $start = microtime(true);

    // Wait until we have output or the timer expired.
    $read  = array($pipes[1]);
    $other = array();
    stream_select($read, $other, $other, 0, $timeout);

    // Get the status of the process.
    // Do this before we read from the stream,
    // this way we can't lose the last bit of output if the process dies between these functions.
    $status = proc_get_status($process);

    // Read the contents from the buffer.
    // This function will always return immediately as the stream is non-blocking.
    $output .= stream_get_contents($pipes[1]);

    if (!$status['running']) {
      // Break from this loop if the process exited before the timeout.
      break;
    }

    // Subtract the number of microseconds that we waited.
    $timeout -= (microtime(true) - $start) * 1000000;

    // Wait 50ms before loop again
    usleep(50000);
  }

  // Check if there were any errors.
  $errors = stream_get_contents($pipes[2]);

  if (!empty($errors)) {
    throw new \Exception($errors);
  }

  // Kill the process in case the timeout expired and it's still running.
  // If the process already exited this won't do anything.
  proc_terminate($process);

  // Close all pipe-streams.
  fclose($pipes[0]);
  fclose($pipes[1]);
  fclose($pipes[2]);

  // Convert multiline-string to array and filter-out empty lines 
  // to be compatible to exec()
  $output = array_filter(explode("\n", $output));

  // Close process and get exitcode
  $exitcode = proc_close($process);
}
?>