PHP, HTML multiple chexbox valuesc

I have got the php, html code. And I want to post the multiple checkbox values, but this does not work dunno why, I can print count or array, it prints(0), does not matter the array values is always empty

<form action = 'main.php?w=creatNewTemplate2' method = 'post'>
    <input type = 'text' name = 'templateName' maxlength = '30'/><br />
    <input type= 'checkbox' name= 'exercises[]' value='A' />A<br />
    <input type= 'checkbox' name= 'exercises[]' value='B' />B<br />
    <input type = 'submit' value = 'Sukurti'/>
</form>

if($w == "creatNewTemplate2")
{
    $d = $_POST['exercises']; 
    $ddd = count($d);
    print_r($_POST);
}