Unexpected PHP script caching behaviour ??

Hi, In every file in our project we do an 'include_once()' at the very top of the file, so that all common constants, global variables and functions are accessible everywhere. Recently we started experiencing from time to time unexpected 'cannot redeclare function xxx' or 'cannot redeclare constant xxx' errors. The strange thing is that it is not an error that happens every time, but sporadically and with no apparent standard of when it happens. We replicated the platform our client has locally, that is, PHP Version 4.0.3pl1 System Windows NT 4.0 build 1381 Server API ISAPI ZEND_DEBUG disabled Thread Safety enabled and I post here two scripts with which to replicate the error: TEST1.PHP ========================== <?php // Define a constant define('TEST1_ALREADY_PROCESSED', 'Yes'); // Declare and set a variable $var1 = "123"; // Define a function function test($var) { echo "Variable: $var"; } ?> TEST2.PHP ========================== <?php // I want all errors and warnings reported error_reporting(E_ALL); // This should give me no problems since the already defined constants // and declared functions and variables would NOT be redeclared // It does not matter if I use 'include', 'include_once', 'require_once', I always // endup with PHP trying to redeclare/redefine things. include_once('test1.php'); // Test if function exists if (function_exists('test')) echo "function test defined<br>\n"; else echo "function test NOT defined<br>\n"; // Test if constant is defined if (defined('TEST1_ALREADY_PROCESSED')) echo "constant TEST1_ALREADY_PROCESSED defined<br>\n"; else echo "constant TEST1_ALREADY_PROCESSED NOT defined<br>\n"; ?> RESULTS ========================= A) In some ocasions the script runs as expected and ALWAYS output the following: function test defined constant TEST1_ALREADY_PROCESSED defined B) But then sometimes the NT server (IIS? PHP?) starts 'caching' elements previously defined in memory so that I got the following results: The first time the script TEST2.PHP runs fine and outputs: function test defined constant TEST1_ALREADY_PROCESSED defined The second time the script is run (and from then on), I got the following output: Warning: Constant test1_already_processed already defined in test1.php on line 3 Fatal error: Cannot redeclare test() in test1.php on line 7 NOTE: I know that the static HTML pages generated by the script are not being cached, and that PHP is indeed re-interpreting the files. In order to proove that I changed the beginning of TEST2.PHP to read as below: <?php echo "Just to test<br>"; // I want all errors and warnings reported error_reporting(E_ALL); . . . ?> And the output started being the following: Just to test Warning: Constant test1_already_processed already defined in test1.php on line 3 Fatal error: Cannot redeclare test() in test1.php on line 7 -- Please HELP!!! Paulo pparola@gst.com.br