PHP Null Coalesce Operator. Available since PHP7, see: https://wiki.php.net/rfc/isset_ternary

null_coalesce_operator_example.php

<?php
error_reporting(-1);
ini_set('display_errors', 1);

$example = ['foo' => ['bar' => 'baz']];

var_dump(
    $example['foo'] ?? []
);

var_dump(
    $example['dummy'] ?? []
);

var_dump(
    $example['foo']['bar'] ?? 'else'
);

var_dump(
    $example['foo']['dummy'] ?? 'else'
);

output.txt

$ build/php-src/sapi/cli/php -v      
PHP 7.0.0-dev (cli) (built: Sep 29 2014 19:00:13) 
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.8.0-dev, Copyright (c) 1998-2014 Zend Technologies

$ build/php-src/sapi/cli/php null_coalesce_operator_example.php
array(1) {
  ["bar"]=>
  string(3) "baz"
}
array(0) {
}
string(3) "baz"
string(4) "else"