unset or change a defined constant PHP

Question

assumed i define a variable like this:

<?php
define("page", "actual-page");
?>

now i have to change this content from actual-page to second-page how can i realize that?

i try the following methods:

<?php
// method 1
    page = "second-page";

// method 2
    define("page", "second-page");

// method 3
    unset(page);
    define("page", "second-page");
?>

now my ideas goes out... what can i do else?

Answer 1

When you use PHP's define() function, you're not defining a variable, you're defining a constant. Constants can't have their value modified once the script starts executing.