title: unset or change a defined constant PHP
body: <p>assumed i define a variable like this:</p>
  
  <pre><code>&lt;?php
  define("page", "actual-page");
  ?&gt;
  </code></pre>
  
  <p>now i have to change this content from <code>actual-page</code> to <code>second-page</code> how can i realize that?</p>
  
  <p>i try the following methods:</p>
  
  <pre><code>&lt;?php
  // method 1
      page = "second-page";
  
  // method 2
      define("page", "second-page");
  
  // method 3
      unset(page);
      define("page", "second-page");
  ?&gt;
  </code></pre>
  
  <p>now my ideas goes out... what can i do else?</p>