client.php

<?php
$e = Exec::withCommandLine($cmd)->launch();
if ($e->getResultCode() !== 0) {
  $message = join("\n", $e->getOutput());
  throw new Exception($message);
}

Exec.php

<?php

class Exec {

  protected $commandLine;
  protected $resultCode = 0;
  protected $stdout;
  protected $stderr;

  public static function withCommandLine($commandLine){
    return new self($commandLine);
  }

  function __construct($commandLine)
  {
    $this->commandLine = $commandLine;
  }

  public function launch()
  {
    $descriptorspec = array(
      ["file", "php://stdin", "r"], // stdin
      ["pipe", "w"],                // stdout
      ["pipe", "w"],                // stderr
    );

    $proc = proc_open($this->commandLine, $descriptorspec, $pipes);
    $this->stdout = array_filter(explode("\n", stream_get_contents($pipes[1])));
    $this->stderr = array_filter(explode("\n", stream_get_contents($pipes[2])));
    fclose($pipes[1]);
    fclose($pipes[2]);
    $this->resultCode = proc_close($proc);

    return $this;
  }

  public function getCommandLine()
  {
    return $this->commandLine;
  }

  public function getResultCode()
  {
    return $this->resultCode;
  }

  public function getStdErr()
  {
    return $this->stderr;
  }

  public function getStdOut()
  {
    return $this->stdout;
  }

  public static function sanitize($input)
  {
    return escapeshellcmd($input);
  }
}