[Rejected] Post buttons; edit, delete, etc

[Meow Purrdock]

I went to edit a post today and have noticed that it no longer works. I tested this on another of my sites which had not been upgraded to the latest version and everything worked then. Once i upgraded everything stopped working. 

The problem itself is in any of the post buttons; edit, report, delete, multiquote, etc. When you click on the button it directs me to an error page. Now, this was fine before I upgraded and now none of the buttons work. 

edit: 
Fatal error: Uncaught Error: Call to undefined function return_bytes() in /storage/ssd4/917/6680917/public_html/editpost.php:912 Stack trace: #0 {main} thrown in /storage/ssd4/917/6680917/public_html/editpost.php on line 912

delete:
Fatal error: Uncaught Error: Call to undefined function return_bytes() in /storage/ssd4/917/6680917/public_html/editpost.php:912 Stack trace: #0 {main} thrown in /storage/ssd4/917/6680917/public_html/editpost.php on line 912

reply:
Fatal error: Uncaught Error: Call to undefined function return_bytes() in /storage/ssd4/917/6680917/public_html/newreply.php:1449 Stack trace: #0 {main} thrown in /storage/ssd4/917/6680917/public_html/newreply.php on line 1449

multiquote:
it does nothing at all. 

report:
does nothing at all. 

newthread and newpost:
atal error: Uncaught Error: Call to undefined function return_bytes() in /storage/ssd4/917/6680917/public_html/newthread.php:1109 Stack trace: #0 {main} thrown in /storage/ssd4/917/6680917/public_html/newthread.php on line 1109

EDIT:I found a fix posted here: https://community.mybb.com/thread-219884.html