PHP 8.x gives this 3 lines errors :
Warning: Attempt to read property “post_author” on null in /home/XXX/wp-content/themes/tempera/functions.php on line 36
Warning: Attempt to read property “post_author” on null in /home/XXX/wp-content/themes/tempera/functions.php on line 36
Warning: Attempt to read property “post_author” on null in /home/XXX/wp-content/themes/tempera/functions.php on line 299
Had to get back to PHP 7.3.4