In php7, what was generally a notice or a deprecated is now a warning : the same level of a mysql error … unacceptable for me.
I do have dozen of old projects and I surely d'ont want to define every variable which I eventually wrote 20y ago.
So two option: let php7 degrade my expensive SSDs writing Gb/hours or implement smthing like server level monitoring ( with auto_[pre-ap]pend_file in php.ini) and turn off E_WARNING
Custom overriding the level of php errors should be super handy and flexible …