stream_select错误：严格标准

I create some socket with stream_socket_client(), and put them in a array named $sockets. When I run the code, an error is coming:

Strict Standards: Only variables should be passed by reference in D:\www\study\cl\s.php on line 63

Code:

while (count($sockets)) {
    $read = $write = $sockets;
    stream_select($read, $write, $e = null, $timeout); //line 63
    if (count($read)) {
        foreach ($read as $r) {
            $id = array_search($r, $sockets);
            $data = fgets($r, 1024);
            echo $data;
            if (strlen($data) == 0) {
                if ($status[$id] == "in progress") {
                    $status[$id] = "failed to connect";
                }
                fclose($r);
                unset($sockets[$id]);
            } else {
                $status[$id] .= $data;
            }
        }
        foreach ($write as $w) {
            $id = array_search($w, $sockets);
            fwrite($w, "HEAD / HTTP/1.0rnHost: " . $host . "rnrn");
            $status[$id] = "waiting for response";
        }
    } else {
        foreach ($sockets as $id => $s) {
            $status[$id] = "timed out " . $status[$id];
        }
        break;
    }
}

This line:

stream_select($read, $write, $e = null, $timeout);

should be:

$e=null;
stream_select($read, $write, $e, $timeout);

While the first code will work, PHP will throw the E_STRICT message. I'm not sure why the PHP developers decided so.

However, you should check the return type of stream_select():

$ret = stream_select($read, $write, $e, $timeout);
if($ret === FALSE) {
    die('Error: stream_select');
}

Once you are checking the return type, you can also use the silence operator @:

$ret = @stream_select($read, $write, $e = NULL, $timeout);
if($ret === FALSE) {
    die('Error: stream_select');
}