[wp-trac] [WordPress Trac] #22239: wp_ob_end_flush_all() tries to destroy non-destroyable output buffers

[WordPress Trac]

#22239: wp_ob_end_flush_all() tries to destroy non-destroyable output buffers
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 Reporter:  dd32                                 |       Owner:  (none)
     Type:  defect (bug)                         |      Status:  new
 Priority:  normal                               |   Milestone:  Future
                                                 |  Release
Component:  Bootstrap/Load                       |     Version:  2.2
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch has-unit-tests dev-        |     Focuses:
  feedback has-test-info                         |
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Changes (by SirLouen):

 * keywords:  has-patch needs-testing has-unit-tests => has-patch has-unit-
     tests dev-feedback has-test-info


Comment:

 == Test Report
 === Description
 ✅ This report validates that the indicated patch works as expected.

 Patch tested: https://github.com/WordPress/wordpress-
 develop/pull/5771.diff

 === Environment
 - WordPress: 6.9-alpha-60093-src
 - PHP: 8.2.28
 - Server: nginx/1.27.5
 - Database: mysqli (Server: 8.4.5 / Client: mysqlnd 8.2.28)
 - Browser: Chrome 136.0.0.0
 - OS: Windows 10/11
 - Theme: Twenty Nineteen 3.1
 - MU Plugins: None activated
 - Plugins:
   * Test Reports 1.2.0

 === Reproduction Steps
 1. First, `zlib.output_compression = 1` should be added to `php.ini` in
 the server. Otherwise, it will not happen. In `wordpress-develop` add it
 to `tools/local-env/php-config.ini`. The OP was referring to New Relic,
 that according to the
 [https://web.archive.org/web/20130117025541/https://newrelic.com/docs/php
 /php-agent-faq Archive], it seems that also deals with zlib.
 2. Now simply add the code attached in Artifacts, wherever it can be
 executed in WP (a plugin, functions.php, you name it)
 3. 🐞 The first part of the code triggers the notice: `( ! ) Notice:
 ob_end_flush(): Failed to send buffer of my_ob_cb (1) in /var/www/src/wp-
 includes/functions.php on line 5470`

 === Expected Results
 - Notice should be handled

 === Actual Results
 1.  ✅ Issue resolved with patch.

 === Additional Notes

 - ⚠️ The only problem is what @kkmuffme mentions: He cannot really unit
 test the error here with `ob_start(callable,0,0)`, because of a limitation
 in PHPUnit. I wonder how this is handled. I suppose that the committer
 should subscribe to the GitHub issue to see if there
 [https://github.com/sebastianbergmann/phpunit/issues/5851 are any changes
 in the future] and update unit tests to remove the skipped part.
 - The original solution by @dd32 was not great because it did not handle
 the problem, it only ignored it.
 - @jorbin, apart from this issue, this patch is ready to be shipped.

 === Supplemental Artifacts

 Code for testing

 {{{
 function my_ob_cb( $output ) {
     return $output;
 }
 ob_start( 'my_ob_cb', 0, 0 );

 function my_ob_cb2( $output ) {
     return $output;
 }
 ob_start( 'my_ob_cb2' );
 echo 'Hello';
 ob_end_flush();
 }}}

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/22239#comment:20>
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