new syntax

Hi, I've been developing a site using PHP (version 3.0.11) on a server that was configured by someone else. I recently installed PHP version 4.0.3 on a different server, and ported my code over to the new machine. Unfortunately it seems that my code is using syntax not recognized by PHP4. I have code like this: echo "<a href=\"http://www.myserver.com/${user_dir}/files/\">click here</a>"; that worked on PHP3, but now I get a parse error until I change it to: echo "<a href=\"http://www.myserver.com/{$user_dir}/files/\">click here</a>"; - note the reversal of the "$" and the "{" This is problematic as I have lots of code that uses that syntax. Am I missing something in my config files that would allow PHP4 to recognize the old PHP3 syntax? I find it hard to believe that PHP4 would not be completely backwards compatible. Any help would be much appreciated. -Dan