I want to study some security vulnerabilities in php 5.2.17, but I can't install it from source, because then I need also all the older versions of all the other application which have something to do with php. How I can install an older version of php in the easiest way? For example in a virtual machine which is compatible with that?
apt-cache policy php5 will show you the available versions on Debian systems. Then you can install with
apt-get install -y php5=whatever_version.
On Fedora deriviatives you can use
yum --showduplicates list php does the same and you can install a specific version using
yum install -y php-whatever_version
If the version you need is not available after running the first command then you need to find and add the repositories that contain the version you are looking for and try again.
After adding a software repository, make sure you do:
apt-get update (Debian)
yum check-update (Fedora_ to update your local package lists or your new software may not show up in the package lists still.