<?php

        define('TEST', 'test#1');
        define('test', 'test#2');

        echo TEST."\n";
        echo test."\n";
?>

Returns

test#1
test

The problem is the fault of zend_constants, which ALWAYS lowercases the define names when they are being stores/retrieved in/from the hash table. The same lowercasing code also causes i18n problems, with defines which do not support the characters in defines made prior to setlocale() function being called. Ref Bug #16865.

The patch below fixes both problems

--- zend_constants.c_old        Sat Jun  8 15:58:01 2002
+++ zend_constants.c    Sat Jun  8 15:58:09 2002
@@ -226,8 +226,6 @@
        lookup_name = do_alloca(name_len+1);
        memcpy(lookup_name, name, name_len+1);

-       zend_str_tolower(lookup_name, name_len);
-
        if (zend_hash_find(EG(zend_constants), lookup_name, name_len+1, (void **) &c)==SUCCESS) {
                if ((c->flags & CONST_CS) && memcmp(c->name, name, name_len)!=0) {
                        retval=0;
@@ -255,7 +253,6 @@
        printf("Registering constant for module %d\n", c->module_number);
 #endif

-       zend_str_tolower(lowercase_name, c->name_len);
        if (zend_hash_add(EG(zend_constants), lowercase_name, c->name_len, (void *) c, sizeof(zend_constant), NULL)==FAILURE) {
                free(c->name);
                if (!(c->flags & CONST_PERSISTENT)