Fail to print out Wireless Snooper result

RouterOS Scripting
1

I would like to display Wireless Snooper result into my project but I get the error message

Array ( [!trap] => Array ( [0] => Array ( [message] => no such command ) ) )

Here is my source code

<?php
	require_once "class.mikrotik.php";

	$api = new routeros_api();
	$api->connect('192.168.88.1','y5admin','y5zone');
	$api->write('/interface/wireless/snooper/interface=wlan1');
	$arr = $api->read();

	print_r($arr);

	$api->disconnect();
?>

I’m using API calling class from

http://wiki.mikrotik.com/wiki/API_PHP_class

2

I updated my script with following code but it doesn’t popup any result in array.

<?php
	require_once "class.mikrotik.php";

	$api = new routeros_api();
	$api->connect('192.168.88.1','admin','admin');
	$api->write('/interface/wireless/snooper/snoop',false);
	$api->write('=interface=wlan1',false);
	$api->write('=once');
	$arr = $api->read();

	print_r($arr);

	$api->disconnect();
?>

And this is the HTML outcome.

Array ( [0] => [1] => [2] => [3] => [4] => [5] => [6] => [7] => [8] => [9] => [10] => )