Why NetBeans complains about PSR-1 violation when assigning returned value?

Question

I have this code:

<?php

function f() {
    return 5;
}

$a = 5;

And I am using NetBeans 8.2 with PSR-1 compatibility check turned on. And I am getting this error:

Why is that and how can I fix it?

Answer 1

The PSR-1 standard states that

Files SHOULD either declare symbols (classes, functions, constants, etc.) or cause side-effects (e.g. generate output, change .ini settings, etc.) but SHOULD NOT do both.

This means if you have function or class definitions in a file, you shouldn't have code with side-effects (like a variable assignment) outside these definitions within the same file.

So

function f() {
    return 5;
}

and

$a = 5;

should be separated into different files.