How do I write a menu using forms for each item that works across several directories?

I am using a header in my website that incorporates a menu that uses forms instead of href so that parameters can be passed. The problem is that when I go into another directory and click on one of the menu link, it tries to find that link in the directory that I am in and not in the root or another directory.

Here is the menu code using href in a directory

          <a href="../index.php" class="active">Home</a>  
          <a href="../membership/join.php"class="joinus">Join Us</a>  
          <a href="../publications/pubs.php?action1=about">About Us</a>

Here is the code in the homepage

          <a href="index.php" class="active">Home</a>  
          <a href="membership/join.php"class="joinus">Join Us</a>  
          <a href="publications/pubs.php?action1=about">About Us</a>

I am looking for a solution where a single menu can be used in the root and directories and sub-directories.