PSR-12 is not checking underscore in variable name

[Eydamos]

According to PSR-12 section 4.3 Properties and Constants

Property names MUST NOT be prefixed with a single underscore to indicate protected or private visibility. That is, an underscore prefix explicitly has no meaning.

I have some old legacy code which still uses underscores like $_aResult = []; but phpcs --standard=PSR12 is not complaining about the underscore.

I'm using phpcs version 3.5.2

[jrfnl]

If I read this:

That is, an underscore prefix explicitly has no meaning.

It basically means that underscore prefixes are allowed in all circumstances and that no check should be done against the property visibility to determine whether an underscore prefix is allowed or not.

So AFAICS, PSR12 handles this correctly.

[Eydamos]

But it states in the first sentence Property names MUST NOT be prefixed with a single underscore so for my understanding you should never ever have an underscore as the first character. The second sentence just clarifies why there MUST NOT be an underscore as an underscore has no meaning

[jrfnl]

You can't just take part of that sentence - please read the sentence as a whole (emphasis in the below quote is mine):

Property names MUST NOT be prefixed with a single underscore to indicate protected or private visibility.

In other words, property names should not be prefixed with an underscore to indicate visibility, but prefixing property names with an underscore for other reasons is fine.

[michalbundyra]

@TrvTimWerdin

Example:

<?php

namespace MyTest;

class A
{
    protected $_a;
}

$ ./bin/phpcs ./example.php --standard=PSR12

FILE: /Users/michalbundyra/Code/PHP_CodeSniffer/example.php
----------------------------------------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------------------------------------
 7 | WARNING | Property name "$_a" should not be prefixed with an underscore to indicate visibility
----------------------------------------------------------------------------------------------------

Time: 343ms; Memory: 6MB

[Eydamos]

So this is only checked for class variables but not for other variables?

<?php

namespace MyTest;

class A
{
    public function foo(): void
    {
        $_result = [];
    }
}

phpcs --standard=PSR-12 ./test.php

Does not give any errors at all

[jrfnl]

So this is only checked for class variables but not for other variables?

The PSR12 rule only applies to properties either way.

[Eydamos]

Ok I will write my own sniff to fix missing rules. Thanks for the quick response

[michalbundyra]

@TrvTimWerdin see Squiz.NamingConventions.ValidVariableName :)