PHP warning: call_user_func_array() expects parameter 1 to be a valid callback

I have the same problem, and I think the issue is in this method declaration, lines 81-83 of feed-json.php:

static public function add_feed_json() {
  add_feed('json', array($this, 'do_feed_json'));
}

If I remove the ‘static’ keyword, it resolves the error. This method is called nonstatically a few lines above in the method add_feed_json_once(), and I think it’s barfing because the $this variable is not available in static functions.

Is there a reason why add_feed_json() is declared to be static? I don’t immediately see any static calls to the function.

I was able to resolve the issue by placing the following line under comments:

//add_action( 'init', array( $this, 'add_feed_json') );

then changed the function to non static as indicated by rohnjeynolds. hope that helps anyone else until the plugin is updated.

The problem is that add_feed_json is marked as static method so there is no $this (object instance variable). Plugin uses singleton pattern, so maybe one way to correct the class would be getting the instance variable with get_instance -method or simply drop all static methods (because there can be only one instance anyways).

how can i fix this problem

<b>Warning</b>: call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in <b>/home/bato.org.tr/httpdocs/wp-includes/plugin.php</b> on line <b>496</b>

I removed the static keyword in public function add_feed_json() and it resolved the error, but im not sure if it perfect solution