Add Null Coalesce Operator

[carusogabriel]

Some to help starts with: https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/2.10/src/Fixer/Operator/TernaryToNullCoalescingFixer.php

Something to also be considering:

if (isset($foo)) {
    $bar = $foo;
} elseif (isset($baz)) {
    $bar = $baz;
} else {
    $bar = 'quux';
}

Already proposed and voted in #9 (comment)

[kukulich]

@carusogabriel I can write the sniff for https://github.com/slevomat/coding-standard, would it be ok?

[carusogabriel]

@kukulich Perfect. I'm not good at sniffers, so I appreciate your help 😄

[kukulich]

Fine, I may write it in the evening if my children and wife allow :)

[kukulich]

Ready for test: slevomat/coding-standard@476b0da

[carusogabriel]

@kukulich This case is already covered? I guess tests are failing here

[kukulich]

Nope, it's not. It's a lot more complicated than simple ternary operator.

[carusogabriel]

@Ocramius @Majkl578 @lcobucci How should we proceed now?

[Ocramius]

Same here: we need a stable release and then we can merge/release as well

[Ocramius]

Manually merged in 2636a26

Thanks @kukulich and @carusogabriel!