How can I update a value of a field depending on outside source?

Question

Say I have a text file or JSON file elsewhere on my domain, that have a simple value, like "yes" or "no". I would like to update a custom field in a database table in Wordpress (postmeta) with the value of that file.

Posts or pages will have a section on them (divi) that will display depending on that value. If it's "yes", then display, if "no", then don't display.

Is there an easy way to do this? From outside WP: This is the preferred way for me, however, can I even do this? How secure is WP?.. I mean.. is it even possible to do this? (injecting the value into a WP table)

From inside WP: I know how to do a simple SQL UPDATE, and I read a little bit on $wpdb. But how do I only make the change if the value is different? (after all, no need to do an update every time a page loads...)

Answer 1

you can read your file using standard PHP:

$value = json_decode( file_get_contents( 'path/to/your/file.json' ) );

Then you can use WordPress function to update post meta:

update_post_meta( $post_id, $meta_name, $value, $prev_value );

$post_id = ID of the post you want to update $meta_name = name of the meta field you want to update $value = new value $prev_value = only posts with this value will be updated (so if you want to only switch yes to no, you can put "yes" there.

If you want to use SQL:

global $wpdb;
$wpdb->query( 
    $wpdb->prepare( 'UPDATE ' $wpdb->prefix . 'postmeta ON meta_value = %s WHERE post_id IN (%s);', $value, join( ',', $post_ids ) )
);

$post_ids = array of all post IDs that should be updated $value = your new value

Answer 2

Do something like this (untested):

function should_it_show() : bool {
    $yes_or_no = json_decode( file_get_contents( 'path/to/your/file.json' ) );
    if ( $yes_or_no === 'yes' ) {
        return true;
    }
    return false;
}

• you said it's a single value for the entire site so post meta doesn't make sense
• an option makes more sense, but that means watching the file and checking it regularly to update that option, that's slow!
• the fastest most efficient way to figure out if you should or should not show, is to read the file and parse the value, the database is a distraction