I get an undefined reference, when I try to link php as
cgi or apache with mod_php.

The configure detects the missing strtok_r:
checking for strtok_r... (cached) no

php_config.h:
/* Define if you have the strtok_r function.  */
/* #undef HAVE_STRTOK_R */

Despite I get the following warnings/errors:
gcc -c php_virtual_cwd.c
php_virtual_cwd.c: In function `virtual_file_ex':
php_virtual_cwd.c:272: warning: implicit declaration of function `strtok_r'
php_virtual_cwd.c:272: warning: assignment makes pointer from integer without a cast
php_virtual_cwd.c:303: warning: assignment makes pointer from integer without a cast

.libs/libphp4.a(php_virtual_cwd.o): In function `virtual_file_ex':
/home/oliver/cvs/cgi/php4/php_virtual_cwd.c:303: undefined reference to `strtok_r'