I'm working on a plugin and trying to build in an option to disable post revisions. I have the setting registered, and confirmed that the checkbox is linking to the database. The option value is either null or 1.

What I want to do is define this constant: define('WP_POST_REVISIONS', false); in the plugin file only if the option is set to 1.

If I put the constant directly into the plugin functions file it works, but if I try and use it in an if statement or through a function, it doesn't work, no matter how I try and do it.

I'm getting the option value like this: $disable_revisions = get_option('disable-revisions');

Here's what I've tried:

if ($disable_revisions==1){
    define('WP_POST_REVISIONS', false);

I also tried using a seperate function:

if ($disable_revisions==1){
    add_action('admin_init', 'disable_revs');

function disable_revs(){
    define('WP_POST_REVISIONS', false);

And I tried adding the action to 'wp', 'init' and a few others too, but none of them work.

How can I define the constant only if $disable_revisions = 1?

1 Answer 1


I don’t think you should define constants in your plugin. It will be very hard to debug later on.

IMHO using wp_revisions_to_keep filter will be much nicer solution.

So your code could look like this:

add_filter( 'wp_revisions_to_keep', 'my_revisions_to_keep_based_on_settings', 10, 2 );

function my_revisions_to_keep_based_on_settings( $num, $post ) {
    // change that according to your needs
    return intval( get_option('disable-revisions') );
  • This works and seems much cleaner than the way I was trying to do it. Thank you!
    – Nexus6
    Jan 29, 2019 at 10:22
  • @Nexus6 yeah, I think it is a much nicer approach to this problem. Jan 29, 2019 at 10:22
  • Constants cannot be re-defined once they are defined. If they could, they wouldn't be 'constant'. (And note that code with a constant in a double-quote string will not be evaluated. All constants in strings must be single-quoted.) Jan 29, 2019 at 18:47
  • @RickHellewell Are you sure you're commenting the correct answer? There are no constants used in my answer ;) Jan 29, 2019 at 18:48
  • 1
    @KrzysiekDróżdż my comment was to the OP; it didn't seem like my comment was an 'answer'. Although I suppose it could be. I just wanted to put the statement (that constants cannot be redefined) for others as a learning thing. And the thing about double quotes is something that I was struggling with just today. I have no issue with your answer. Jan 29, 2019 at 18:51

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