Description:
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It was great to see the addition of the nil-coalescing operator in PHP 7, but one case that I encounter a lot but still appears to have no solution is calling a method on a variable that may be null.

What I'd like to propose is a new nullable method calling operator, which would enable us to call a method on a variable that may be null; if the variable is null the method call is ignored and null is returned, otherwise the method is called and its result returned. My proposed operator for this would be `?->`, i.e- a normal method operator, but with a question mark after the variable indicating that the developer is aware it could be null. Put of another way, if `->` is "call method", then `?->` "call method if not null".

We could then use this like so:

`$array = $object?->getFoo()?->getArray() ?? [];`

Here we use the operator to try to drill down into `$object`, seeking out an array. If either `$object` or `$object->getFoo()` returns `null`, then null is returned, triggering the nil coalescing operator and resulting in a default empty array.

NOTE: This operator only handles `null` cases, i.e- if any of the methods above are called upon an object that doesn't have them, then an error is thrown as normal.