Access variable from parent PHP function

Question

Is it possible to obtain a variable from a parent function without declaring that function in parenthesis when calling the function (not possible in this instance).

function list_posts($filter_by_date){

    /* Dome things to do first 8*/
    function filter(){
        /* Do something that involves the variable $filter_by_date */
    }
}

Answer 1

You can use closures:

function list_posts($filter_by_date){

    /* Dome things to do first 8*/
    $filter = function() use($filter_by_date) {
        echo $filter_by_date; // outputs "test"

        /* Do something that involves the variable $filter_by_date */
    };

    $filter();
}

list_posts("test");