Error in compiling PHP with PostgreSQL support

Dear all,

I can compile PHP 4.0.6 with Postgres 7.1.3 successfully.  However,
when  I try to start apache, an error comes out:

Cannot load /usr/local/apache/libexec/libphp4.so into server:
/usr/local/apache/libexec/libphp4.so: undefined symbol:
pg_encoding_to_char

I would like to ask how can I solve it.

Thanks in advance.

Regards
Cosmos