The constants true/false (and certainly other pre-defined constants) are not defined when PHP is called from apache, but they are when PHP is called in command line !

here is a test script: test.php
<?php
var_dump(PHP_VERSION, true, TRUE);
?>

1- on command line : C:\php>php test.php
outputs :
string(9) "4.3.0-dev"
bool(true)
bool(true)

2- but called from apache : http://localhost/test.php
it outputs :
string(11) "PHP_VERSION"
string(4) "true"
string(4) "TRUE"

see the constants are no more booleans but strings !

I'm using PHP 4.3.0 alpha 2
with Apache 1.3.24