Error - Warning: Cannot modify header information - headers already sent by

Question

Error:

Warning: Cannot modify header information - headers already sent by (output started at /home/ya3mblog/public_html/wp-login.php:59) in /home

Answer 1

In my case happened because from the Wordpress Rest API in the functions I was ending the job by doing

echo json_encode($result);

instead of the simple:

return $result;

Changing that.. worked!