One way to do this is to have your main version of php set up with mod_php and run all of the others through fast cgi on different ports (i.e. 81, 82, 83 etc). This won't guarantee totally consistent behavior though.

Having multiple instances of apache + php never really tickled my fancy, but it probably the easiest way to do it. If you don't feel like KISS ... here's an idea.

Get your apache up and running, and try do configure it like debian and ubuntu do it, eg, have directories for loaded modules. Your apache conf can use lines like this:

Include /etc/apache2/mods-enabled/*.load
Include /etc/apache2/mods-enabled/*.conf

Then build your first version of php, and give it a prefix that has the version number explicitly contained, eg, /usr/local/php/5.2.8, /usr/local/php/5.2.6 ...

The conf/load would look something like this:

php5.2.6.load

LoadModule php5_module /usr/local/php/5.2.6/libphp5.so

php5.2.8.load

LoadModule php5_module /usr/local/php/5.2.8/libphp5.so

To switch versions, all you have to do is change the load and conf files from the directory apache does the include on for the ones for another version. You can automate that with a simple bash script (delete the actual file, copy the alternate versions file in place, and restart apache.

One advantage of this setup is the everything is consitent, so long you keep the php.ini's the same in terms of options and modules (which you would have to do with CGI anyway). They're all going through SAPI. Your applications won't need any changes whatsoever, nor need to use relative URLs.

I think this should work, but then again, i haven't tried it, nor am i likely to do so as i don't have the same requirements as you. Do comment if you ever do try though.

I have just successfully downgraded from PHP5.3 on Ubuntu 10.

To do this I used the following script:

#! /bin/sh
php_packages=`dpkg -l | grep php | awk '{print $2}'`


sudo apt-get remove $php_packages


sed s/lucid/karmic/g /etc/apt/sources.list | sudo tee /etc/apt/sources.list.d/karmic.list


sudo mkdir -p /etc/apt/preferences.d/


for package in $php_packages;
do echo "Package: $package
Pin: release a=karmic
Pin-Priority: 991
" | sudo tee -a /etc/apt/preferences.d/php
done


sudo apt-get update


sudo apt-get install $php_packages

For anyone that doesn't know how to run scripts from the command line, here is a brief tutorial:

1. cd ~/
2. mkdir bin
3. sudo nano ~/bin/myscriptname.sh
4. paste in the script code I have posted above this
5. ctrl+x (this exits and prompts for you to save)
6. chmod u+x myscriptname.sh

These 6 steps create a script in a folder called "bin" in your home directory. You can then run this script by calling the following command:

~/bin/myscriptname.sh

Oulia!

Hope this helps some of you!

For reference, here is where I got the script: PHP5.2.10 for Ubuntu 10

There are several people on there all confirming that this works, and it worked a treat for me.

Understanding that you're probably talking about a local/desktop machine and would probably like to continue talking about a local/desktop machine, I'll throw an alternative out there for you just in case it might help you or someone else:

Set up multiple virtual server instances in the cloud, and share your code between them as a git repository (or mercurial, I suppose, though I have no personal experience all you really need is something decentralized). This has the benefit of giving you as close to a production experience as possible, and if you have experience setting up servers then it's not that complicated (or expensive, if you just want to spin a server up, do what you need to do, then spin it down again, then you're talking about a few cents up to say 50 cents, up to a few bucks if you just leave it running).

I do all of my project development in the cloud these days and I've found it much simpler to manage the infrastructure than I ever did when using local/non-virtualized installs, and it makes this sort of side-by-side scenario fairly straight forward. I just wanted to throw the idea out there if you hadn't considered it.

With CentOS, you can do it using a combination of fastcgi for one version of PHP, and php-fpm for the other, as described here:

https://web.archive.org/web/20130707085630/http://linuxplayer.org/2011/05/intall-multiple-version-of-php-on-one-server

Based on CentOS 5.6, for Apache only

1. Enable rpmforge and epel yum repository

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm
wget http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
sudo rpm -ivh rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm
sudo rpm -ivh epel-release-5-4.noarch.rpm

2. Install php-5.1

CentOS/RHEL 5.x series have php-5.1 in box, simply install it with yum, eg:

sudo yum install php php-mysql php-mbstring php-mcrypt

3. Compile and install php 5.2 and 5.3 from source

For php 5.2 and 5.3, we can find many rpm packages on the Internet. However, they all conflict with the php which comes with CentOS, so, we’d better build and install them from soure, this is not difficult, the point is to install php at different location.

However, when install php as an apache module, we can only use one version of php at the same time. If we need to run different version of php on the same server, at the same time, for example, different virtual host may need different version of php. Fortunately, the cool FastCGI and PHP-FPM can help.

Build and install php-5.2 with fastcgi enabled

1) Install required dev packages

yum install gcc libxml2-devel bzip2-devel zlib-devel \
curl-devel libmcrypt-devel libjpeg-devel \
libpng-devel gd-devel mysql-devel

2) Compile and install

wget http://cn.php.net/get/php-5.2.17.tar.bz2/from/this/mirror
tar -xjf php-5.2.17.tar.bz2
cd php-5.2.17
./configure --prefix=/usr/local/php52 \
--with-config-file-path=/etc/php52 \
--with-config-file-scan-dir=/etc/php52/php.d \
--with-libdir=lib64 \
--with-mysql \
--with-mysqli \
--enable-fastcgi \
--enable-force-cgi-redirect \
--enable-mbstring \
--disable-debug \
--disable-rpath \
--with-bz2 \
--with-curl \
--with-gettext \
--with-iconv \
--with-openssl \
--with-gd \
--with-mcrypt \
--with-pcre-regex \
--with-zlib
make -j4 > /dev/null
sudo make install
sudo mkdir /etc/php52
sudo cp php.ini-recommended /etc/php52/php.ini

3) create a fastcgi wrapper script

create file /usr/local/php52/bin/fcgiwrapper.sh

#!/bin/bash
PHP_FCGI_MAX_REQUESTS=10000
export PHP_FCGI_MAX_REQUESTS
exec /usr/local/php52/bin/php-cgi
chmod a+x /usr/local/php52/bin/fcgiwrapper.sh
Build and install php-5.3 with fpm enabled


wget http://cn.php.net/get/php-5.3.6.tar.bz2/from/this/mirror
tar -xjf php-5.3.6.tar.bz2
cd php-5.3.6
./configure --prefix=/usr/local/php53 \
--with-config-file-path=/etc/php53 \
--with-config-file-scan-dir=/etc/php53/php.d \
--enable-fpm \
--with-fpm-user=apache \
--with-fpm-group=apache \
--with-libdir=lib64 \
--with-mysql \
--with-mysqli \
--enable-mbstring \
--disable-debug \
--disable-rpath \
--with-bz2 \
--with-curl \
--with-gettext \
--with-iconv \
--with-openssl \
--with-gd \
--with-mcrypt \
--with-pcre-regex \
--with-zlib


make -j4 && sudo make install
sudo mkdir /etc/php53
sudo cp php.ini-production /etc/php53/php.ini


sed -i -e 's#php_fpm_CONF=\${prefix}/etc/php-fpm.conf#php_fpm_CONF=/etc/php53/php-fpm.conf#' \
sapi/fpm/init.d.php-fpm
sudo cp sapi/fpm/init.d.php-fpm /etc/init.d/php-fpm
sudo chmod a+x /etc/init.d/php-fpm
sudo /sbin/chkconfig --add php-fpm
sudo /sbin/chkconfig php-fpm on


sudo cp sapi/fpm/php-fpm.conf /etc/php53/

Configue php-fpm

Edit /etc/php53/php-fpm.conf, change some settings. This step is mainly to uncomment some settings, you can adjust the value if you like.

pid = run/php-fpm.pid
listen = 127.0.0.1:9000
pm.start_servers = 10
pm.min_spare_servers = 5
pm.max_spare_servers = 20

Then, start fpm

sudo /etc/init.d/php-fpm start

Install and setup mod_fastcgi, mod_fcgid

sudo yum install libtool httpd-devel apr-devel
wget http://www.fastcgi.com/dist/mod_fastcgi-current.tar.gz
tar -xzf mod_fastcgi-current.tar.gz
cd mod_fastcgi-2.4.6
cp Makefile.AP2 Makefile
sudo make top_dir=/usr/lib64/httpd/ install
sudo sh -c "echo 'LoadModule fastcgi_module modules/mod_fastcgi.so' > /etc/httpd/conf.d/mod_fastcgi.conf"
yum install mod_fcgid

Setup and test virtual hosts

1) Add the following line to /etc/hosts

127.0.0.1 web1.example.com web2.example.com web3.example.com

2) Create web document root and drop an index.php under it to show phpinfo switch to user root, run

mkdir /var/www/fcgi-bin
for i in {1..3}; do
web_root=/var/www/web$i
mkdir $web_root
echo "<?php phpinfo(); ?>" > $web_root/index.php
done

Note: The empty /var/www/fcgi-bin directory is required, DO NOT REMOVE IT LATER

3) Create Apache config file(append to httpd.conf)

NameVirtualHost *:80


# module settings
# mod_fcgid
<IfModule mod_fcgid.c>
idletimeout 3600
processlifetime 7200
maxprocesscount 17
maxrequestsperprocess 16
ipcconnecttimeout 60
ipccommtimeout 90
</IfModule>
# mod_fastcgi with php-fpm
<IfModule mod_fastcgi.c>
FastCgiExternalServer /var/www/fcgi-bin/php-fpm -host 127.0.0.1:9000
</IfModule>




# virtual hosts...


#################################################################
#1st virtual host, use mod_php, run php-5.1
#################################################################
<VirtualHost *:80>
ServerName web1.example.com
DocumentRoot "/var/www/web1"


<ifmodule mod_php5.c>
<FilesMatch \.php$>
AddHandler php5-script .php
</FilesMatch>
</IfModule>


<Directory "/var/www/web1">
DirectoryIndex index.php index.html index.htm
Options -Indexes FollowSymLinks
Order allow,deny
Allow from all
</Directory>


</VirtualHost>
#################################################################
#2nd virtual host, use mod_fcgid, run php-5.2
#################################################################
<VirtualHost *:80>
ServerName web2.example.com
DocumentRoot "/var/www/web2"


<IfModule mod_fcgid.c>
AddHandler fcgid-script .php
FCGIWrapper /usr/local/php52/bin/fcgiwrapper.sh
</IfModule>


<Directory "/var/www/web2">
DirectoryIndex index.php index.html index.htm
Options -Indexes FollowSymLinks +ExecCGI
Order allow,deny
Allow from all
</Directory>


</VirtualHost>
#################################################################
#3rd virtual host, use mod_fastcgi + php-fpm, run php-5.3
#################################################################
<VirtualHost *:80>
ServerName web3.example.com
DocumentRoot "/var/www/web3"




<IfModule mod_fastcgi.c>
ScriptAlias /fcgi-bin/ /var/www/fcgi-bin/
AddHandler php5-fastcgi .php
Action php5-fastcgi /fcgi-bin/php-fpm
</IfModule>


<Directory "/var/www/web3">
DirectoryIndex index.php index.html index.htm
Options -Indexes FollowSymLinks +ExecCGI
Order allow,deny
Allow from all
</Directory>


</VirtualHost>

4) restart apache. visit the 3 sites respectly to view phpinfo and validate the result. ie:

http://web1.example.com
http://web2.example.com
http://web3.example.com

If all OK, you can use one of the 3 virtual host as template to create new virtual host, with the desired php version.

Note: The following method will work on windows.

An alternative method (if it is ok to run a single version of PHP at a time) is to define multiple Apache services, each of which will use a different PHP version.

First of all use conditions in the Apache configuration file:

 <ifdefine php54>
SetEnv PHPRC C:/apache/php54/
ScriptAlias /php/ "C:/apache/php54/"
AddType application/x-httpd-php .php
Action application/x-httpd-php "/php/php-cgi.exe"
</ifdefine>


<ifdefine php55>
SetEnv PHPRC C:/apache/php55/
ScriptAlias /php/ "C:/apache/php55/"
AddType application/x-httpd-php .php
Action application/x-httpd-php "/php/php-cgi.exe"
</ifdefine>

Now using the httpd.exe create two separate services from command line (elevated to administrator):

httpd.exe -k install -n Apache224_php54 -D php54


httpd.exe -k install -n Apache224_php55 -D php55

Now you can start one of the above services at a time (should shutdown one before starting the other).

If you have previously installed Apache as service you can remove that using below command (replace the service name with the one you have used):

apache -k uninstall -n Apache224

One further note is that I personally use a "notification area icon program" called "Seobiseu" to start and stop services as needed. I have added the two above services to it.

Rasmus Lerdorf, who created PHP, is maintaining an active Vagrant solution that seems to solve your needs. It allows for quickly switching between PHP versions, currently supporting more than 20 different versions. It comes out of the box with an nginx server, but can easily be switched to apache2 with a preconfigured setting. It also supports MySQL out of the box.

This way you will have access to all versions of PHP, deployable on two of the main web servers, in a nice vagrant box, maintained by the big man behind PHP.

For more information I would like to refer to the talk given by mr. Lerdorf at https://youtu.be/6XnysJAyThs?t=2864

The github repository containing the Vagrant solution is found at https://github.com/rlerdorf/php7dev

For testing I just run multiple instances of httpd on different IP addresses, so I have php7 running on 192.168.0.70 and php5.6 running on 192.168.0.56. In production I have a site running an old oscommerce running php5.3 and I just have a different conf file for the site

httpd -f /etc/apache2/php70.conf
httpd -f /etc/apache2/php53.conf

It's also a clean way to have different php.ini files for different sites. If you just have a couple of sites if a nice way to keep things organized and you don't have to worry about more then 1 site at a time when you upgrade something

I have several projects running on my box. If you have already installed more than one version, this bash script should help you easily switch. At the moment I have php5, php5.6, and php7.0 which I often swtich back and forth depending on the project I am working on. Here is my code.

Feel free to copy. Make sure you understand how the code works. This is for the webhostin. my local box my mods are stored at /etc/apache2/mods-enabled/

    #!/bin/bash
# This file is for switching php versions.
# To run this file you must use bash, not sh
#
# OS: Ubuntu 14.04 but should work on any linux
# Example: bash phpswitch.sh 7.0
# Written by Daniel Pflieger
# growlingflea at g mail dot com


NEWVERSION=$1  #this is the git directory target


#get the active php enabled mod by getting the array of files and store
#it to a variable
VAR=$(ls /etc/apache2/mods-enabled/php*)


#parse the returned variables and get the version of php that is active.
IFS=' ' read -r -a array <<< "$VAR"
array[0]=${array[0]#*php}
array[0]=${array[0]%.conf}




#confirm that the newversion veriable isn't empty.. if it is tell user
#current version and exit
if [ "$NEWVERSION" = "" ]; then
echo current version is ${array[0]}.  To change version please use argument
exit 1
fi


OLDVERSION=${array[0]}
#confirm to the user this is what they want to do
echo "Update php"  ${OLDVERSION} to ${NEWVERSION}




#give the user the opportunity to use CTRL-C to exit ot just hit return
read x


#call a2dismod function: this deactivate the current php version
sudo a2dismod php${OLDVERSION}


#call the a2enmod version.  This enables the new mode
sudo a2enmod php${NEWVERSION}


echo "Restart service??"
read x


#restart apache
sudo service apache2 restart