title: Can not create SSH tunnel with PHP function ssh2_tunnel
body: <p>I'm using PHP 5.6 with ssh2 extension to create SSH tunnel to a remote host, here is my code:</p>
  
  <pre><code>$connection = ssh2_connect($host[0], 22);
  if (ssh2_auth_password($connection, $host[1], $host[2])) {
  if ($tunnel = ssh2_tunnel($connection, '127.0.0.1', 1080)){
   //curl commands
   }
  }
  </code></pre>
  
  <p>I can do some Linux commands working with <code>ssh2_exec</code> but can not create SSH tunnel with <code>ssh2_tunnel</code>, here the error logs:</p>
  
  <blockquote>
    <p>PHP Warning:  ssh2_tunnel(): Unable to request a channel from remote host </p>
  </blockquote>
  
  <p>Anybody can give me some hints?</p>