I have this error (in errors.log or debug mode) on every page :
Warning: Cannot modify header information - headers already sent by (output started at /home/www/dirname/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php:89) in /home/www/dirname/vendor/cakephp/cakephp/src/Database/Driver/PDODriverTrait.php on line 92
Warning (2): Cannot modify header information - headers already sent by (output started at /home/www/dirname/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php:89) [CORE/src/Database/Driver/Mysql.php, line 136]
The site has a lot of visitors and works perfectly well. Nobody reported any problem.
Strange …