Very interesting problem...this published regexp:
^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{4,8}$
was working with my PHP4.3.0 on Win32 platform
and on 4.3.0 on RedHat8.0 (all RH patches installed).
However, this regexp is NOT working on RedHat 9
with Apache 2.0.  Any ideas why?

Gives REG_BADRPT message....Simple regexp's DO work.

This regexp compiles if you remove the ?'s (but of 
course...will not do what I want it to!)...and of course
the string is:

$regexp="^(?=.*\\d)(?=.*[a-z])(?=.*[A-Z]).{4,8}\$";

taken directly from http://regexlib.com

BTW:  libiconv 1.8 is installed.  mbstring is loaded 
and all encodings are set to UTF8...yes, ereg is not 8 bit safe...know that...hope this ain't the problem.

4.3.1 was compiled with --with-regex=system...however, it appears to use "bundled" regexp anyway. (tried with regex=php and regex=system...both produce same results..ie. used bundled regexp library).

this is NOT an Apache problem....php CGI version produces same results...even though somewhere in the depths I read "php must be compiled with the same regexp version as apache if php loaded as module".  I hear what this is saying, but I don't understand how to determine this...and, like I said...CGI version produces same result.

Mayble I'll try --with-regexp=apache...see what happens...

If this is the same thing as Bug #1683...sorry...please combine with that one....but...I'm not sure it's the same.

any response may be helpful...HLP!