Description:
------------
I am initiating a socket to an SMTP server to send a message. After transmitting the EHLO, I need to wait for a variable number of lines to be returned, so I am using a do{..}while() loop to check if there is nothing more to be read from the socket before sending the next command.  The program, however, falls into an endless wait because socket_read() is never returning an empty string (like the documentation says it will) or FALSE (like some other bug reports say it will).

I have tried with both the PHP_BINARY_READ and PHP_NORMAL_READ flags set as well as with no flags set at all.

Reproduce code:
---------------
foreach($mail_head as $in) {
  $output = "";
  $in .= "\r\n";
  echo $in;
  @socket_write($socket, $in, strlen($in)) or die("Error writing to socket: " . socket_strerror(socket_last_error()));
  do {
    $out = false;
    $out = socket_read($socket, 1024);
    $output .= $out;
  } while($out !== false && $out !== '');
  if(!preg_match('/^[23]/', $output)) {
    die("Error: Mail server did not return the expected response.");
  }
}

Expected result:
----------------
EHLO fake.domain
250-this server offers 4 extensions
250-AUTH LOGIN
250-SIZE 30485760
250-HELP
250 AUTH=LOGIN
MAIL FROM:<address@fake.domain>
250 Requested mail action okay, completed
...

Actual result:
--------------
EHLO fake.domain
<nothing>