Null coalescing operator

The Null coalescing operator (??) is a syntactical sugar, but a important one. Previously in PHP5 when we were having some variable which could be undefined, we used the ternary operator as follows:

$username = isset($_GET['username']) ? $_GET['username'] : '';

However, now in PHP7, we can simply write:

$username = $_GET['username'] ?? '';

Although this is just a syntactical sugar, it can save time and make code cleaner.