call_user_func_array() expects parameter 1 to be a valid callback

I get below errors

<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>wp-includesplugin.php</b> on line <b>505</b><br />

Below is the line at line 505
call_user_func_array($the_[‘function’], array_slice($args, 0, (int) $the_[‘accepted_args’]));

Notice: Undefined variable: this in wp-contentpluginsfeed-jsonfeed-json.php on line 82

Below is the line at line 82
add_feed(‘json’, array($this, ‘do_feed_json’));

Thanks.

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