I haven't used that app (so I don't know if the advise is sound) ... but there is a CentOS built (though unsupported) version of php-5 in the CentOSPlus repository:
http://mirror.centos.org/centos/4/centosplus/Readme.txt
Unsupported is a relative term ... it is a better fit for CentOS-4 than just about any other way to get php-5.
If you are going to enable the centosplus repo, I highly recommend that you read:
man yum.conf
And that you set up the centosplus section of /etc/yum.repos.d/CentOS- Base.repo with a line like this:
installonlypkgs=php*
(if you want other packages from the CentOS Plus repo, also add them to the install only section using spaces between packages)
Also, I would put this line in the [base] and [updates] sections of the file:
exclude=php*
(excluding any other centosplus packages is also recommended ... again, spaces between packages on the exclude line in the [base] and [updates] repo)
There are also instructions in the Readme.txt file that discuss php- domxml .. that file does not exist in php-5.x so you have to remove it by hand to upgrade.
Thanks Johnny - I had a good read of 'teh Internets' and opted for an install of 4.4.2 and this seems to have fixed the problem with SugarCRM (subject to some final testing).
I had to wade through quite a few dependency errors during the configure and make but the forum thread below was extremely useful:
http://www.vbulletin.com/forum/archive/index.php/t-114170.html