[horde] php and phphorde rpms

[Bianchi Quota Leonardo]

Hi, I'm using on a RedHat 7.3 box HORDE and IMP.
 
Installed packets: php-4.2.2-0horde3; php-devel-4.2.2-0horde3;
php-mcrypt-4.2.2-0horde3; php-ldap-4.2.2-0horde3
php-imap-4.2.2-0horde3; libmcrypt-2.5.6-0horde2;
php-mysql-4.2.2-0horde3; horde-2.2.3-1 and imp-3.2.1-1.
 
Now I would like to install on the same box another webmail application
(squirrelmail) which uses php (redhat original rpm is
php-4.1.2-7.i386.rpm)
 
For this new installation I will use a basic implementation. this means
no mysql, no ldap.
 
Do you think this could be a problem, i.e. in IMAP/squirrelmail
communications? 
How could I manage?
 
Thanks!
 
Leonardo.