how to retrieve post_id under woocommerce_add_to_cart_validation hook?

Question

I am trying to retrieve post id under custom_fields_validation() function but I am receiving the following

error: Trying to get property of non-object on line 116

add_action('woocommerce_add_to_cart_validation','custom_fields_validation'), 10, 3 );



public static function custom_fields_validation() 
    { 

    global $post;

if(isRecurring($post->ID)){
if ( empty( $_POST['inputday']) ){
            wc_add_notice( __( 'Please select field 1;', 'woocommerce' ), 'error' );
            return false; 
        }
        if ( empty( $_POST['inputtime'] )){
            wc_add_notice( __( 'Please select field 2;', 'woocommerce' ), 'error' );
            return false; 
        }
}           
    return true;
    }

Answer 1

woocommerce_add_to_cart_validation passes the product id as the second argument to the callback function, so you can access it like this:

function custom_fields_validation( $passed_validation, $product_id ) { 
    if( isRecurring( $product_id ) ) {
        if ( empty( $_POST['inputday']) ){
            wc_add_notice( __( 'Please select field 1;', 'woocommerce' ), 'error' );
            return false; 
        }
        if ( empty( $_POST['inputtime'] )){
            wc_add_notice( __( 'Please select field 2;', 'woocommerce' ), 'error' );
            return false; 
        }
    }

    return $passed_validation;
}
add_filter( 'woocommerce_add_to_cart_validation', 'custom_fields_validation', 10, 2 );

Also, note that woocommerce_add_to_cart_validation is a filter, not an action, so I've used apply_filters instead of add_action. I also fixed a syntax error, where you had an extra parentheses after 'custom_fields_validation'.

I also updated the function to return the current validation state. Otherwise you could be returning true even if a previous validation had failed.