如何在PHP中找到套接字的本地端口？

I am creating a UDP socket using:

$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);

When I use socket_getsockname to get the socket name:

   /**
    * Get Source port (Refactored to allow unit testing)
    *
    * @return string
    */
    private static function getSourcePort($sock)
    {
        $addr = null;
        $port = null;
        socket_getsockname($sock, $addr, $port);
        return $port;
    }

The port returned is always 0 and the addr is 0.0.0.0

How to get the bound port properly?

Binding the socket after creation fixed the issue:

if (socket_bind($sock, $sourceIp) === false)
{
    $failReason = "socket_bind() failed: reason: " . socket_strerror(socket_last_error());
}

// get the source port
$sourcePort = 0;
if (socket_getsockname($sock, $sourceIp, $sourcePort) === false)
{
    $failReason = "socket_getsockname() failed: reason: " . socket_strerror(socket_last_error());
}