Fatal error: Uncaught Error: Call to undefined function wp_convert_hr_to_bytes()

Hey guys

Hope everyone is fine. I did a cleaning of my domain (cause my website had been hacked) and as such i had to download all my website files, examine them to see which are intruders and upload the fiene ones back on the domain.
The issue is that after doing that, i had this annoying error displayed :

Fatal error: Uncaught Error: Call to undefined function wp_convert_hr_to_bytes() in /htdocs/wp-includes/default-constants.php:33 Stack trace: #0 /htdocs/wp-settings.php(41): wp_initial_constants() #1 /htdocs/wp-config.php(85): require_once(‘/htdocs/wp-sett…’) #2 /htdocs/wp-load.php(37): require_once(‘/htdocs/wp-conf…’) #3 /htdocs/wp-blog-header.php(13): require_once(‘/htdocs/wp-load…’) #4 /htdocs/index.php(17): require(‘/htdocs/wp-blog…’) #5 {main} thrown in /htdocs/wp-includes/default-constants.php on line 33

I’ve been searching the web for a solution, but till now, i found nothing. I’m desperate and my client is getting angrier the more.
Please for help and thanks in advance !

The page I need help with: [log in to see the link]