FC5 SELinux prevents php from connecting to postgresql. I had a hard time trying to figure out why I could not connect from php to postgres locally in a new and patched FC5 box, although I could connect to that same postgres server and with the same user from another box (FC3).
From /var/log/messages:
kernel: audit(1151945653.900:39): avc: denied { name_connect } for pid=17167 comm="httpd" dest=5432 scontext=user_u:system_r:httpd_t:s0 tcontext=system_u:object_r:postgresql_port_t:s0 tclass=tcp_socket Regards, Clodoaldo Pinto