undefined Symbol PQoidValue

I have recently upgraded PHP to the latest version, and also upgraded Postgres to the latest version. PHP worked fine after it's upgrade, but after the Postgres upgrade it is now broken. I have recompiled & installed PHP, but when I try & start Apache, I get the following error message: Syntax error on line 224 of /usr/local/apache/conf/httpd.conf: Cannot load /usr/local/apache/libexec/libphp4.so into server: /usr/local/apache/libexec/libphp4.so: undefined symbol: PQoidValue I have explicitly told php where to look for the postgres libs with the --with-psql=/usr/local/postgres/lib option and I still get the same error message. What might be causing it?