why can't I upgrade php?

I am trying to upgrade to the latest stable php, and I get the following message with rpm -Uvh php-4.3.4-1.1.i386.rpm (even if I try the --force tag).

warning: php-4.3.4-1.1.i386.rpm: V3 DSA signature: NOKEY, key ID 30c9ecf8
error: Failed dependencies:
       php = 4.3.3-6 is needed by (installed) php-imap-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-ldap-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-mysql-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-odbc-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-pgsql-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-domxml-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-snmp-4.3.3-6
       php = 4.3.3-6 is needed by (installed) php-xmlrpc-4.3.3-6

I get a similar error if I try to erase (rpm -e) the old php file.

What am I doing wrong?