PHP has recently launched its new version i.e. PHP 8 and it consists of many new features, constructor property promotion is one of the new features introduced in PHP 8. In previous versions of PHP(~7.*), we used to define our variables as class property and assign its value in the constructor
PHP 7 brings a new rather handy feature null coalescing operator. This new feature is similar to the ternary operator that we were using in older versions of PHP (PHP 5 & greater)
I would like to explain the Scalar type declaration feature, I hope this will help you to improve your knowledge and help you somehow in the future.