In PHP 8.1 there is a lot of depreciated.
I made a list that may not be exhaustive:
trim(): Passing null to parameter #1 ($string) of type string is deprecated
explode(): Passing null to parameter #2 ($string) of type string is deprecated
strlen(): Passing null to parameter #1 ($string) of type string is deprecated
strtolower(): Passing null to parameter #1 ($string) of type string is deprecated
Function strftime() is deprecated
Deprecated: str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated
SimpleXMLElement::__construct(): Passing null to parameter #2 ($options) of type int is deprecated
mb_strtolower(): Passing null to parameter #1 ($string) of type string is deprecated
Most can be corrected with this ?? ''
But not Strftime () for example
Regards