I am searching for any info/tutorial etc on how to display errors.
For instance, when I save a custom metabox - I would like to validate the data and send a message back to the user if the input was invalid.
I have found plenty of instructions on how to save a post - but NONE of them describe how to report invalid data to the user.
It also seems that the WP_ERROR construct is not what I am looking for. All I would like to do is when invalid data or some other error is found is to include a notice on the page that indicates what is not correct.
Any resources that someone could point me to would be most appreciated.