Apache unique Vhost user, PHP sessions not working

I am looking to run an number of Apache server which will host websites for multiple clients. I have installed the libapache2-mpm-itk module and have created unique users/groups for each clients set of files. And configured their corresponding vhost file to run the process with that user/group.

<IfModule mpm_itk_module>
      AssignUserId www-client www-client1
</IfModule>

This works fine until I try to use PHP sessions. In the vhost file I have also added a custom session save path.

php_admin_value session.save_path "/var/www/html/client1/_php/session"

A PHP script is able to generate session files in the directory with the following permissions but isn’t able to read them:

-rw------- www-client1 www-client1

A full example of my vhost is:

<VirtualHost *:443>
   ServerName client1.com
   ServerAlias client1.com www.client1.com
   DocumentRoot /var/www/html/client1/www
   ErrorLog /var/www/logs/client1/www-error.log
   CustomLog /var/www/logs/client1/www-access.log combined
   php_admin_value error_log "/var/www/logs/client1/www-error.php.log"

   <Directory /var/www/html/client1/www>
      Options None
      AllowOverride None
      Order Deny,Allow
      Allow from All
   </Directory>

   <IfModule mpm_itk_module>
      AssignUserId www-client1 www-client1
   </IfModule>

   php_admin_value log_errors 1
   php_admin_value open_basedir "/var/www/html/client1"
   php_admin_value upload_tmp_dir "/var/www/html/client1/_php/upload_tmp"
   php_admin_value session.save_path "/var/www/html/client1/_php/session"
   php_admin_value soap.wsdl_cache_dir "/var/www/html/client1/_php/soap_cache"

   SSLEngine On
   SSLCertificateFile /var/www/certs/client1/www.crt
   SSLCertificateKeyFile /var/www/certs/client/www.key
</VirtualHost>

I’m running Apache 2.4.41,PHP 7.4.3 on Ubuntu 20.04 and there are no errors being outputted to any of my log files.

Any ideas/suggestions on this and further enhancements would be very much appreciated.

Answer

After a lot of Googling I have found a solution.

I also needed to ensure that php-fpm was installed and adding the following lines of configuration to the Apache VHost pointing to a unique PHP FPM socket per user fixed my issue.

<FilesMatch .php$>
   SetHandler "proxy:unix:/run/php/php-fpm-client1.sock|fcgi://localhost"
</FilesMatch>

My PHP FPM configuration file looks like:

vi /etc/php/X/fpm/pool.d/client1.conf
[client1]
  
user = www-client1
group = www-client1
listen = /run/php/php-fpm-client1.sock
listen.owner = www-client1
listen.group = www-client1
pm = dynamic
pm.max_children = 5
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 3
php_admin_value[log_errors] = 1
php_admin_value[error_log] = "/var/www/logs/client1/php-error.log"
php_admin_value[open_basedir] = "/var/www/html/client1"
php_admin_value[session.save_path] = "/var/www/html/client1/_php/session"

bash /etc/init.d/php*-fpm restart

I also found that all php_admin_value values defined in the VHost needed to be moved to the FPM pool.