<?PHP
function get($socket,$length=1024){
    $send = '';
    $sr = fgets($socket,$length);
    while( $sr ){
        $send .= $sr;
        if( $sr[3] != '-' ){ break; }
        $sr = fgets($socket,$length);
    }
    return $send;
}
function put($socket,$cmd,$length=1024){
    fputs($socket,$cmd."\r\n",$length);
}
if (!($smtp = fsockopen("smtp.gmail.com",$errno,$errstr,15))) {
    die("Unable to connect");
}
echo "<PRe>\n";
echo get($smtp); // should return a 220 if you want to check

$cmd = "EHLO ${_SERVER['HTTP_HOST']}";
echo $cmd."\r\n";
put($smtp,$cmd);
echo get($smtp); // 250

$cmd = "STARTTLS";
echo $cmd."\r\n";
put($smtp,$cmd);
echo get($smtp); // 220
if(false == stream_socket_enable_crypto($smtp,true,STREAM_CRYPTO_METHOD_TLS_CLIENT)){
    // fclose($smtp); // unsure if you need to close as I haven't run into a security fail at this point
    die("unable to start tls encryption");
}

$cmd = "EHLO ".$_SERVER['HTTP_HOST'];
echo $cmd;
put($smtp,$cmd);
echo get($smtp); // 250

$cmd = "QUIT";
echo $cmd."\r\n";
put($smtp,$cmd);
echo get($smtp);

echo "</pre>";

fclose($smtp);