[wp-trac] [WordPress Trac] #40787: REST API: Attempts to output headers without confirming headers have not been sent

[WordPress Trac]

#40787: REST API: Attempts to output headers without confirming headers have not
been sent
--------------------------+-----------------------------
 Reporter:  kraftbj       |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  REST API      |    Version:
 Severity:  normal        |   Keywords:
  Focuses:  rest-api      |
--------------------------+-----------------------------
 The `rest_handle_deprecated_function` and
 `rest_handle_deprecated_argument` functions fire `header()` without
 confirming if headers have already been sent or not.

 This can result in PHP warnings, which depending on the site's settings,
 will output into the REST API response, which breaks JSON.

 {{{
 Error: Warning: Cannot modify header information - headers already sent by
 (output started at /public_html//wp-includes/functions.php:3720) in
 /public_html/wp-includes/rest-api.php on line 492
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/40787>
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