I was looking for a lightweight PHP framework. Some projects just don't want the frameworks with heavy footprint, like zend does. 

PHP Fat-Free Framework may be the one that wins in this category. I will post some update after I try it out.

Maybe they had it before, but I just noticed this today, that we can install more than one versions of PHP, and then use eselect to switch the version.

In short, we can set in /etc/make.conf:

PHP_TARGETS="php5-3 php-5-2"
PHP_INI_VERSION=production

Then call eselect to see what php versions we have available in apache:

# eselect php list apache2 

Without "PHP_INI_VERSION=production", a dev version of php.ini will be installed.

I found this guy http://www.atoomnet.net/php/  offers the RPM and SRPM for the more recent php packages on CentOS.

Another one here: http://www.jasonlitka.com, or http://www.jasonlitka.com/media/SRPMS/ for the SRPM.

To install the PECL package uploadprogress on CentOS, we do:

1. Yum up some packages:
   # yum install php-pear php-devel httpd-devel
2. Install uploadprogress through PEAR:
   # pear install pecl/uploadprogress
3. Tell PHP to load uploadprogress:
   # echo extension=uploadprogress.so > /etc/php.d/uploadprogress.ini
4. Restart Apache:
   # /sbin/service httpd graceful

1. Yum up some packages:
   yum install make php-pear php-devel httpd-devel
2. Install APC using pear (the pear installer is smarter than the pecl installer):
   When the installer asks about APXS, say ‘no’. 
   pear install pecl/apc
3. Tell PHP to load APC:
   echo extension=apc.so > /etc/php.d/apc.ini
4. Edit the file /etc/php.d/apc.ini, and add the following lines:
   apc.ttl="7200"
   apc.user_ttl="7200"
   apc.shm_segments="3"

Here are some references on plotting using PHP:

• AJAX and PHP SVG Charting Demo 
• Image_Graph wiki
• Graphing in SVG with the PEAR Image_Graph Package 
• PHPLOT

Make the following changes to /etc/php.ini:

# Do not expose PHP error messages to external users
display_errors = Off

# Enable safe mode
safe_mode = On

# Only allow access to executables in isolated directory
safe_mode_exec_dir = php-required-executables-path

# Limit external access to PHP environment
safe_mode_allowed_env_vars = PHP_

# Restrict PHP information leakage
expose_php = Off

# Log all errors
log_errors = On

# Do not register globals for input data
register_globals = Off

Install lighttpd and php

1. Read http://gentoo-wiki.com/HOWTO_Lighttpd and decide which USE flags you will need. Write those flags into /etc/portage/package.use. Since I plan to use fastcgi and php, I do have at least these two flags set.
2. Check php installation. If php was installed but cgi USE flag was off, you have to reinstall php with "USE=cgi".
3. Now install lighttpd:
   # emerge -v lighttpd
4. Among the few opcode cache for php, xcache is quite stable on lighttpd. So install that:
   

Adjust the parameters

Having installed APC for PHP does not automatically improve the performance. You have to adjust the parameters. At the very least, change these values:

apc.ttl="7200"
apc.user_ttl="7200"
apc.shm_segments="3"
apc.shm_size="90"

Setting apc.ttl and apc.user_ttl to none-zero can ensure that the cached php code gets refreshed at the given number of seconds without filling up the memory with stale entries.