Sniff for multiline string concatenation

[jaymcp]

Our string concatenation rules only currently check whether there is an appropriate amount of whitespace around the operator (i.e. 1 space before and after the .). We do not currently test beyond that, so the following code is considered valid:

<?php

$string = 'foo'
. "\n" .
'bar';

I would argue that this is incorrect; I would expect the above code to be considered valid only if it was formatted as per the one of the examples below:

<?php

$string = 'foo' . "\n" . 'bar';

// or

$string = 'foo'
    . "\n"
    . 'bar';

Would it be valuable to folks if we added a Sniff for this style of concatenation, or are we happy to rely upon code review?

[jrmd]

I think this one should be implemented, we would likely flag this on code review to be changed so we might as well add a sniff for it.

[ampersarnie]

I think this would be a great addition.