I'm using Apache/1.3.11 (Unix) PHP/3.0.15 mod_ssl/2.5.0 OpenSSL/0.9.4 along with MySQL 3.22.32.

Apache came with OpenBSD and everything else was compiled from the ports tree. Here's the error I see in the Apache logs after loading up a friends Prometheus code.

/usr/libexec/ld.so: Undefined symbol "_pthread_key_create" called from httpd:/usr/local/lib/mysql/libmysqlclient.so.6.0 at 0x402ba530

A little <? echo "Hello!"; ?> statement doesn't break it though. I did see a message after going through a few searching that might have something to do with the problem.  You can check the thread out at http://x23.deja.com/getdoc.xp?AN=589913288&CONTEXT=953816431.2085158958&hitnum=7

Here's the jist of it:

        "I noticed, as of mysql 3.22.32, any code that you link to -lmysqlclient needs to be linked to -lc_r also
This may be a bug in the current linker, not giving you an error when you don't do this.  Libmysqlclient calls some stuff in the libc_r"

I ran /sbin/ldconfig -m /usr/local/lib/mysql before I started MySQL and I still have the problem.

Running 'ldconfig -r' yields:

        28:-lc_r.2.1 => /usr/lib/libc_r.so.2.1
        32:-lmysqlclient.6.0 => /usr/local/lib/mysql/libmysqlclient.so.6.0