PHP configure:
./configure --with-mysql=/usr/local
--with-apache=../apache_1.3.17 --enable-track-vars
--enable-bcmath --disable-debug --with-pfpro

The debug.log that follows the configure:
gcc -o conftest -g -O2   -R/usr/local/lib/mysql
-L/usr/local/lib/mysql -R/usr/local/lib -L/usr/local/lib
conftest.c -lpfpro -lmysqlclient -lm -lcrypt  1>&5

/usr/local/lib/libpfpro.so: undefined reference to
`pthread_mutex_unlock'
/usr/local/lib/libpfpro.so: undefined reference to
`pthread_self'
/usr/local/lib/libpfpro.so: undefined reference to
`pthread_mutex_destroy'
/usr/local/lib/libpfpro.so: undefined reference to
`pthread_mutex_lock'
/usr/local/lib/libpfpro.so: undefined reference to
`pthread_mutex_init'

When I put -pthread in CFLAGS, I did not receive this error,
and both php and apache compiled, but when apache was
started, it kept spawning more processes, and ate resources
until I did a 'killall -KILL httpd'