title: SO_KEEPALIVE for PHP stream sockets
body: <p>How to set SO_KEEPALIVE for php stream sockets?
  Is there any function similar to <code>setsockopt</code> with <code>SO_KEEPALIVE</code> option?</p>
  
  <p>I am creating a server stream socket with SSL added to its context.
  Currently my server is unable to find out when a client terminated its connection abnormally(say, client gets crashed).</p>