Backreferences are not working in the suplied regex functions.  The documentation says they are Posix 1003.2 compliant but you can't use a simple expresion like 
ereg("(.+)=\1","foo=foo",$m), it will never match It should be a) implemented to be Posix compliant or b) warned in the documentation. The only backreference usable is in ereg_replace, where you can use it in the substituion expresion. I talked to other people and they have the same problem.