New sniff: add comma after last param in multi-line function calls

[jrfnl]

Sniff basics	-
Fixable for PHP:	7.3+
Sniff type:	Modernize
Fixer type:	Safe

Short description

As of PHP 7.3, a trailing comma will be allowed after the last parameter in a function call and in calls to isset() and unset().
This is mostly useful to keep a clean code history when using multi-line calls with each parameter on a new line.

Related PHPCompatibility sniff(s):

• NewTrailingComma (PHP 7.3: new sniff to detect trailing comma's in function calls, isset() and unset() PHPCompatibility#632)

PHP manual references:

• https://wiki.php.net/rfc/trailing-comma-function-calls

Example code:

Detect the following code pattern(s):

unset(
    $somethingIDontNeedAnymore,
    $anotherOneToKill,
    $letsMakeThisEasy
);

echo $twig->render(
    'index.html',
    compact(
        'title',
        'body',
        'comments'
    )
);

$newArray = array_merge(
    $arrayOne,
    $arrayTwo,
    ['foo', 'bar']
);

var_dump(
    $whatIsInThere,
    $probablyABugInThisOne,
    $oneMoreToCheck
);

$text = sprintf(
    $en,
    'comma',
    'Jane'
);

And fix these to:

unset(
    $somethingIDontNeedAnymore,
    $anotherOneToKill,
    $letsMakeThisEasy,
);

echo $twig->render(
    'index.html',
    compact(
        'title',
        'body',
        'comments',
    ),
);

$newArray = array_merge(
    $arrayOne,
    $arrayTwo,
    ['foo', 'bar'],
);

var_dump(
    $whatIsInThere,
    $probablyABugInThisOne,
    $oneMoreToCheck,
);

$text = sprintf(
    $en,
    'comma',
    'Jane',
);

Notes for implementation of the sniff:

• Only apply this change to multi-line calls where each parameter is on a new line (nr of parameters === the diff in line number of the function call T_STRING and the closing parenthesis).
• Beware of trailing comments after the last parameter!
• Trailing comma's are also allowed in calls to closures and methods.