Can wp_insert_post_data filter be used to save custom field data?

Question

I have custom field data that I would like to modify on its way to the database.

wp_insert_post_data filter seems to be the closest thing I can find to achieving this. I dumped the $data and $postarr values but I don't see how I can access my custom field data as those fields aren't in the dump.

Can wp_insert_post_data be used to save custom field data, and if not, what is the preferred filter / practice?

EDIT: additional detail:

I have a front end form that asks for a user's company website address. If the user simply types in 'example.com' then the target for that website in his post defaults to mywebsite.com/example.com instead of opening up example.com.

If http:// is not part of the text they enter, then I want to add that to it right before it saves. There is javascript to help with validation, but those who have it turned off get by it.

Answer 1

You can access the raw $_POST data from the wp_insert_post_data filter, but there are probably better ways to intercept that data.

• save_post or similar hook would probably work
• As you are dealing with post_meta, update_post_meta uses update_metadata which provides the update_{$meta_type}_meta and updated_{$meta_type}_meta filters. Those may be the best for you but your question is shy on detail so I can't be sure.

Based on the edit, use the update_{$meta_type}_meta filter. Your question is still light on detail but the following filter should dump all of the data so you can at least see what you are dealing with:

add_filter(
  'update_post_meta',
  function($meta_type,$object_id,$meta_key,$meta_value,$prev_value) {
    var_dump($meta_type,$object_id,$meta_key,$meta_value,$prev_value);
    die;
  },
  10,5
);

Note: that will break your site but not permanently. It is purely for debugging/development. It is just to give you a glance at the data that comes through the filter.