Call custom function in function.php using woocommerce wordpress

[admin]

I am trying to call a custom function in function.php on POST submit button in wordpress.
Bellow you can see if statement when i remove it function call work's perfectly but with if statement it's not work when I am post i am reached in if statement but not able to call the function.

if (isset($_POST['addcustomcarts']))

    {
        echo("if");
    add_filter('woocommerce_before_cart', 'customcart');
    //global $woocommerce;

    function customcart() {
    global $woocommerce;
    $my_post = array(
      'post_title'    => 'My post',
      'post_content'  => 'This is my post.',
      'post_status'   => 'publish',
      'post_author'   => 1,
      'post_type'     =>'product'
    );
    echo"sdafsdf";
    // Insert the post into the database
     $product_ID=wp_insert_post( $my_post );

     add_post_meta($product_ID, '_regular_price', 100, $unique);
     add_post_meta($product_ID, '_price', 100, $unique);
      add_post_meta($product_ID, '_stock_status', 'instock', $unique);



    $woocommerce->cart->add_to_cart( $product_ID, $quantity=1 );


    //exit;
    //header("Location: http://www.mydomain.com");exit();
    wp_redirect(".home_url('cart').");
    //wp_redirect(home_url());

    //global $wpdb;
    //$wpdb->query
    //exit;
    //exit;
    }

    }