On CentOS 6.x 32-bit

wget http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
rpm -Uvh remi-release-6*.rpm epel-release-6*.rpm

On CentOS 6.x x86_64 (64-bit)

wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
rpm -Uvh remi-release-6*.rpm epel-release-6*.rpm

screenshot:

Step 3 – Now enable your newly added Remi repo. Open the /etc/yum.repos.d/remi.reporepository file using a text editor of your choice – I use Nano:

nano /etc/yum.repos.d/remi.repo

Step 4 – Edit enabled=0 line to enabled=1:

4.a – Update to PHP 5.4, in [remi] section:

4.b – Update to PHP 5.5, in [remi-php55] section:

4.c – Bonus  – Update to PHP 5.6 (beta version), in [remi-php56] section:

once done, Save changes (Control+O) and exit (Control+X)

Step 5 – Now update yum:

yum update -y

Step 6 – Done. Now you can check using this command:

php -v

In this example I got:

PHP 5.4.28

PHP 5.5.12

PHP 5.6.0 Beta 2

Now you can test your PHP script on your browser and hope everything still runs smoothly.

PREVENTING THE MESS

You may have to edit old httpd.conf and php.conf (if your srcipt went messed up).

Step 1 – Make backup of php.conf file:

mv /etc/httpd/conf.d/php.conf /etc/httpd/conf.d/php.conf.bak

Step 2 – Then edit httpd.conf  file:

nano /etc/httpd/conf/httpd.conf

Step 3 – You have to find every line with php  in it, and remove it (or simply add #). If you have found out that there is at least one line per domain, so be sure to remove them all. Once done, save and exit.

Step 4 – Finally restart httpd service (Apache):

service httpd restart

Also, you may also want to upgrade MySQL using this command:

mysql_upgrade -u root -p