What does the syntax "foo()($parameter)" signify in PHP?

The syntax "foo()($parameter)" in PHP signifies that the function foo() is being called and then immediately invoked with the parameter $parameter. This is known as a function returning a function, where the initial function call returns a closure that is then immediately invoked with the provided parameter. Example PHP code snippet implementing the fix:

function foo() {
    return function($parameter) {
        echo "Parameter value: " . $parameter;
    };
}

foo()("Hello, World!");