- Ondrej php5-oldstable packages, would be a good option, but at the moment they don't work on Saucy Salamander (debphp.org/ubuntu-saucy-support.html). You could just wait.
- You can compile PHP on your own.
- Easy solution would be to temporarly switch to old (raring) repositories, install PHP (5.4), Apache (2.2), etc and lock package versions (so it won't be upgraded anymore):
Please consider it as a risky operation, as you might loose your settings and break your system. I did not test all the lines, so please tell me if I have to adjust something
# upgrade system, so you can add to ignore all updates later
sudo apt-get update
sudo apt-get upgrade
# remove your php, apache, etc
sudo apt-get purge apache2 php5 libapache2-mod-php5 # add here your server packages
# change repositories to raring (with backup)
sudo sed -i.bak "s/saucy/raring/g" /etc/apt/sources.list
# update and install server packages
sudo apt-get update
sudo apt-get install apache2 php5 libapache2-mod-php5 phpmyadmin #add here packages you need and make sure you install php5.4 and apache2.2
# change repositories back to saucy
sudo sed -i "s/raring/saucy/g" /etc/apt/sources.list
# ignore all current upgrades (package hold)
sudo apt-mark hold `aptitude -F%p --disable-columns search ~U`
