Named argument default causes improper formatting

Example function:
```php
function foo($label, $default = null) {
}
```

example function call:
```php
foo(
	label: 'bar',
	default: 'baz',
);
```

which then gets reformatted like so:
```php
foo(
	label: 'bar',
default
	: 'baz',
);
```

I would imagine there are many other keywords which I believe are valid named arguments but would cause the same issue.