PHP Null Coalesce Assignment Operator

在PHP 7 版本之前，?: 這種寫法稱為，「Ternary Operator」: $data = isset($data) ? $data : 'hello';

PHP 7 之後，??這種寫法稱為「Null Coalescing Operator」: $data = $data ?? 'hello'; 可以不用多判斷isset

PHP 7.4 之後寫法更簡潔，??=這種寫法稱為「Null Coalesce Assignment Operator」: $data ??= 'hello';

本筆記參考: 1. https://stackoverflow.com/questions/59102708/what-is-null-coalescing-assignment-operator-in-php-7-4 2. https://caloskao.org/php-null-coalescing-operator/