$ P = ''? "1": $ p; what is the problem with defining variables like this?

$ P? 1: $ p; what is the problem with variable definition? Why is there no problem when I run it in my company? copy it to my computer. because my & p is used as the page number, every function has the first error in $ p.

Reply to discussion (solution)

May I ask the landlord p = $ p = ''? "1": $ p; are you using a trielement operation?

$ P = ''? "1": $ p;
There will be a Notice: Undefined variable: p error warning
The reason is that you have not blocked E_NOTICE-level errors, that is, your program is not robust.

Loose syntax:
$ P = @ $ p = ''? "1": $ p;
The strict statement is:
$ P =! Isset ($ p) | $ p = ''? "1": $ p;

Php7 writability
$ P = $ p ?? "1 ";

Thanks 2L. So happy. $ P solved the problem.
However, there are still many Notice: Undefined problems. It turns out that the gap between changing computers is so big.

Error_reporting (E_ALL ^ E_NOTICE) in the program );
Error_reporting = E_ALL ^ E_NOTICE in php. ini
Then, Notice: Undefined will be gone.