How to upgrade from php4 to php5 on CentOS 4

This is surprisingly difficult to find out how to do. You can’t just type “yum update php” as CentOS 4.4 only has php4 in its base repository. Php5 does exist in the centosplus repository but you need to configure yum to allow this to be used. The basic instructions for doing this are:

yum install yum-plugin-priorities

This installs the priority plugin which allows you to chose to only upgrade the packages from centosplus that you want. In this case php.

Next open

nano /etc/yum.repos.d/CentOS-Base.repo


You should have something that looks like this.

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
priority=1

#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
#baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4


You now need to enable the centosplus repositiory. Also make sure that the priority is 2. It should now look like this.

[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
priority=2
protect=1


Now you need to exclude php from all the other active repositories so that php5 from centosplus is installed. This is done by adding the following line to each of the other repository

exclude=php*


The final file should look like this.

# CentOS-Base.repo
#
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#

#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
#baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
priority=2
protect=1


Save the changes and update

yum update


You should see that centosplus is now part of your repositories and see something like the following

update 100% |=========================| 951 B 00:00
base 100% |=========================| 1.1 kB 00:00
centosplus 100% |=========================| 951 B 00:00
addons 100% |=========================| 951 B 00:00
extras 100% |=========================| 1.1 kB 00:00


Yum should finally prompt you to install the updates for php5. Don’t forget to restart apache to change it from using php4 to php5.

Updates:
A couple of quick things to note with upgrading:
1. php4 PEAR::MAIL is not compatible with php5 so you will need to upgrade it as well.
2. Your apache php.conf file will be overwritten. This last issue caught me out as I had apache set up to parse .html for php includes – the upgrade disable this. I guess the moral is test, test and test again after upgrading.