I´m trying to do specific action when the user add to cart for a WooCommerce Variation product.

This is my code inside a Class :

My Class {
    ...

    public function init(){
        add_action('woocommerce_add_to_cart', array( $this, 'custom_add_to_cart' ), 10 );
    }

    function custom_add_to_cart() {
        global $woocommerce;
        if( !empty( $_POST )
            && !empty( $_POST['product_id'] )
            && !empty( $_POST['variation_id'] )
        ){
            if( !WC()->cart->is_empty() ){
                WC()->cart->empty_cart( true );
            }
            var_dump( $_POST );
            WC()->cart->add_to_cart( $_POST['product_id'], 1, $_POST['variation_id'] );
            exit;
        }

    }

}  

For some reasons, when I click on "add to cart" button, my function is called several times, maybe inside a loop until to get this error :

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 262144 bytes) ....

What I should do to call this function just once ?