XCache is a open-source opcode cacher, which means that it accelerates the performance of PHP on servers. It optimizes performance by removing the compilation time of PHP scripts by caching the compiled state of PHP scripts into the shm (RAM) and uses the compiled version straight from the RAM. This will increase the rate of page generation time by up to 5 times as it also optimizes many other aspects of php scripts and reduce serverload.

Step # 1: Download xcache source code

Use wget command to download latest stable release:
# cd /opt
# wget http://xcache.lighttpd.net/pub/Releases/1.2.1/xcache-1.2.1.tar.gz

Step # 2: Untar tar ball

Use tar command:
# tar -zxvf xcache-1.2.1.tar.gz
# cd xcache-1.2.1


Step # 2: Compile and install xcahce

Use phpize command to prepare xcache as a PHP extension for compiling:
# phpize
Configure, compile and install xcache:
# ./configure --enable-xcache
# make
# make install

Default xcache.so installation location

• 64 bit PHP module installed at /usr/lib64/php/modules/xcache.so
• 32 bit PHP module installed at /usr/lib/php/modules/xcache.so

Step # 3: Create xcache.ini file

Under RHEL / CentOS, you place php modules configuration at /etc/php.d/ directory:
# cd /etc/php.d/
Create xcache.ini file:
# vi xcache.ini
Append configuration directives:

[xcache-common]
; change me - 64 bit php => /usr/lib64/php/modules/xcache.so
; 32 bit php => /usr/lib/php/modules/xcache.so
zend_extension = /usr/lib64/php/modules/xcache.so

[xcache.admin]
xcache.admin.auth = On
xcache.admin.user = "mOo"
; xcache.admin.pass = md5($your_password)
xcache.admin.pass = ""

[xcache]
xcache.shm_scheme =        "mmap"
xcache.size  =               32M
xcache.count =                 1
xcache.slots =                8K
xcache.ttl   =              3600
xcache.gc_interval =         300

; Same as aboves but for variable cache
; If you don't know for sure that you need this, you probably don't
xcache.var_size  =            0M
xcache.var_count =             1
xcache.var_slots =            8K
xcache.var_ttl   =             0
xcache.var_maxttl   =          0
xcache.var_gc_interval =     300

; N/A for /dev/zero
xcache.readonly_protection = Off

xcache.mmap_path =    "/dev/zero"

xcache.cacher =               On
xcache.stat   =               On

Save and close the file.

Alternatively, you can also copy default xcache.ini to /etc/php.d/
# cp xcache.ini /etc/php.d/
# vi /etc/php.d/xcache.ini

Restart your Apache web server:
# service httpd restart

If you are using Lighttpd web server, enter:
# service lighttpd restart

Step # 4: Make sure xcache is working

Type the following command for verification:
$ php -v
Output:

PHP 5.1.6 (cli) (built: Nov 20 2007 11:11:52)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
    with XCache v1.2.1, Copyright (c) 2005-2007, by mOo