title: PHP: Why isn't exec() returning output?
body: <p>I'm writing a PHP script to be used to check for network connections with Linux shell command <code>ping</code> calling it with PHP's <code>exec()</code>:</p>
  
  <pre><code>&lt;?php
  
  
  // Bad IP domain for testing.
  $domain_bad = "lksjdflksjdf.com";
  
  $ip_address = $domain_bad;
  
  exec("ping -c 1 $domain_bad", $output, $return_var);
  
  var_dump($return_var);
  echo "return_var is: $return_var" . "\n";
  var_dump($output);
  
  
  exit;
  ?&gt;
  </code></pre>
  
  <p>I'm not getting the output for the error message from ping in <code>$output</code> which is what I'm expecting:</p>
  
  <pre><code>$ php try.php
  ping: unknown host lksjdflksjdf.com
  int(2)
  return_var is: 2
  array(0) {
  }
  </code></pre>
  
  <p>If the domain is a good domain, such as yahoo.com, then <code>$output</code> has the output from ping in an array. But if it's an error such as <code>'ping: unknown host lksjdflksjdf.com'</code> it doesn't get returned to the <code>$output</code> array.</p>
  
  <p>Why is this happening and is there a better method to do this? </p>