One requirement for this instruction to work is you need PHP 5.3. I have tried to patch PHP 5.2.17 according to PHP-FPM website but it didn't work. After tried to patch it so many times, I decided to upgrade to PHP 5.3.5 and it works correctly now.

Also, when compile PHP-FPM, you will get 2 PHP files. One is "php" which is for CLI mode and "php-fpm" which is PHP-FPM. "php-cgi" file won't be compiled until you removed "--enable-fpm" from configuration. That means... if you want to have the rest of Virtualhosts to run with mod_fcgid (php-cgi) with PHP 5.2, you can still do that. Just make sure to upgrade directly to PHP 5.3 and PHP-FPM at the same time. Always have "--enable-fpm" in configuration file for PHP to compile. That way, "php-cgi" will not compile in PHP version 5.3. So, all websites run with mod_fcgid that still use "php-cgi" file still run in PHP 5.2.

In case you need all of them to run in PHP 5.3. You need to compile PHP twice, one with "--enable-fpm" and one without it.

1. Enable PHP-FPM and compile PHP.

1.1 Copy "configure.php5" for custom compile

mkdir -p /usr/local/directadmin/custombuild/custom/suphp
cp /usr/local/directadmin/custombuild/configure/suphp/configure.php5 /usr/local/directadmin/custombuild/custom/suphp

1.2 Edit configure.php5

nano -w /usr/local/directadmin/custombuild/custom/suphp/configure.php5

add "--enable-fpm" into the file. After edit, the "configure.php5" will look like below :

#!/bin/sh
"./configure" \
"--prefix=/usr/local/php5" \
"--enable-force-cgi-redirect" \
"--enable-fastcgi" \
"--with-config-file-path=/usr/local/etc/php5/cgi" \
"--with-curl=/usr/local/lib" \
"--with-gd" \
"--with-gettext" \
"--with-jpeg-dir=/usr/local/lib" \
"--with-freetype-dir=/usr/local/lib" \
"--with-kerberos" \
"--with-mcrypt" \
"--with-mhash" \
"--with-mysql=/usr" \
"--with-mysqli=/usr/bin/mysql_config" \
"--with-pcre-regex=/usr/local" \
"--with-pdo-mysql=/usr" \
"--with-pear=/usr/local/lib/php" \
"--with-png-dir=/usr/local/lib" \
"--with-zlib" \
"--with-zlib-dir=/usr/local/lib" \
"--with-openssl" \
"--with-iconv=/usr/local" \
"--enable-bcmath" \
"--enable-calendar" \
"--enable-exif" \
"--enable-ftp" \
"--enable-gd-native-ttf" \
"--enable-magic-quotes" \
"--enable-soap" \
"--enable-sockets" \
"--enable-mbstring" \
"--enable-zip" \
"--enable-wddx" \
"--enable-fpm"

1.3 Compile PHP

cd /usr/local/directadmin/custombuild
./build php n

Note : If you get error while compile, you may need to run " .build clean " and then try to compile again.

1.4 After compiled, you will see where PHP-FPM file located as below :

.....
Make Complete
Copying php.ini..
/usr/local/etc/php5/cgi/php.ini already exists, skipping.
Installing php...
Installing PHP SAPI module:       fpm
Installing PHP CLI binary:        /usr/local/php5/bin/
Installing PHP CLI man page:      /usr/local/php5/man/man1/
Installing PHP FPM binary:        /usr/local/php5/sbin/
Installing PHP FPM config:        /usr/local/php5/etc/
Installing PHP FPM man page:      /usr/local/php5/man/man8/
Installing build environment:     /usr/local/php5/lib/php/build/
Installing header files:          /usr/local/php5/include/php/
Installing helper programs:       /usr/local/php5/bin/
  program: phpize
  program: php-config
Installing man pages:             /usr/local/php5/man/man1/
  page: phpize.1
  page: php-config.1
Installing PEAR environment:      /usr/local/lib/php/
.....

2. Now, Create Init script file

2.1 Copy file from source

cp /usr/local/directadmin/custombuild/php-5.3.5/sapi/fpm/init.d.php-fpm.in /etc/init.d/php-fpm
chmod 755 /etc/init.d/php-fpm

2.2 Edit php.fpm init script file as below:

nano -w /etc/init.d/php-fpm

Edit php.fpm file FROM :

.....
prefix=@prefix@
exec_prefix=@exec_prefix@
 
php_fpm_BIN=@sbindir@/php-fpm
php_fpm_CONF=@sysconfdir@/php-fpm.conf
php_fpm_PID=@localstatedir@/run/php-fpm.pid
 
 
php_opts="--fpm-config $php_fpm_CONF"
.....

TO :

.....
prefix=/usr/local/php5
exec_prefix=${prefix}
 
php_fpm_BIN=/usr/local/php5/sbin/php-fpm
php_fpm_CONF=/usr/local/php5/etc/php-fpm.conf
php_fpm_PID=/var/run/php-fpm.pid
 
 
php_opts="--fpm-config $php_fpm_CONF"
.....
 

You may need to run command below to have PHP-FPM run automatically when start up (After reboot or turn on the machine) :

/sbin/chkconfig php-fpm on

2.3 Edit PHP-FPM configuration file to match your need. My example below is just to make it work but you can adjust to whatever you like :

nano -w /usr/local/php5/etc/php-fpm.conf

Below is my "php-fpm.conf" configuration :

[global]
pid = /var/run/php-fpm.pid
error_log = /var/log/php-fpm.log
[admin]
listen = /fcgi/admin/public_html/admin.sock
listen.owner = $pool
listen.group = $pool
listen.mode = 0666
user = $pool
group = $pool
pm = dynamic
pm.max_children = 50
pm.start_servers = 3
pm.min_spare_servers = 3
pm.max_spare_servers = 10
php_admin_value[open_basedir] = /home/$pool/:/tmp:/var/tmp:/var/www/html

Note 1 : $pool is variable which will replaced by the data from the bracket. Here, that is "admin".
Note 2 : php_admin_value[open_basedir] is not require but suggested. Also, without "/var/www/html", you won't be access your webmail or anything through domain name. However, you can still access webmail or anything through IP Address.

2.4 Try to start / stop / restart PHP-FPM

service php-fpm start
service php-fpm stop
service php-fpm restart

Note :

1. To have PHP-FPM compiled and configured in this tutorial doesn't mean you already using it. It just means you already have PHP-FPM ready to use. You need to check my tutorial [HOW-TO] DirectAdmin - Run Apache with "mod_fcgid on PHP 5.2 / 5.3" and "mod_fastcgi + PHP-FPM on 5.3" on the same server that will be post soon.

Source :
- http://php.net/manual/en/install.fpm.php
- http://michaelshadle.com/2010/08/26/cleanest-configuration-for-the-new-php-fpm
- http://php-fpm.org