How to Enable APC With PHP on CentOS 6.3

The Alternative PHP Cache (APC) is a robust, open-source framework that optimizes and caches PHP intermediate code. It’s a PECL extension, sharing the packaging and distribution system with its sister, PEAR.

This tutorial will guide you through the process of enabling APC (Alternative PHP Cache) to enhance the speed of PHP on your server.

Whether you’re using a dedicated server, a VPS server, or even cloud hosting or shared hosting, APC can be a valuable addition to your PHP environment.

Step 1: Install APC using the yum command

To install APC, you’ll need to use the yum command. Here’s the command you need to enter:

[root@centos63 ~]# yum install php-pecl-apc -y

After running this command, the system will resolve dependencies and install the necessary packages. Once the installation is complete, you’ll see a message indicating that php-pecl-apc and php-pear have been installed.


[root@centos63 ~]# yum install php-pecl-apc -y
Loaded plugins: fastestmirror, presto
Loading mirror speeds from cached hostfile
 * base:
 * extras:
 * updates:
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package php-pecl-apc.i686 0:3.1.9-2.el6 will be installed
--> Processing Dependency: /usr/bin/pecl for package: php-pecl-apc-3.1.9-2.el6.i686
--> Processing Dependency: /usr/bin/pecl for package: php-pecl-apc-3.1.9-2.el6.i686
--> Running transaction check
---> Package php-pear.noarch 1:1.9.4-4.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

 Package               Arch            Version                  Repository                     Size
 php-pecl-apc          i686            3.1.9-2.el6              CentOS6.3-Repository           96 k
Installing for dependencies:
 php-pear              noarch          1:1.9.4-4.el6            CentOS6.3-Repository          393 k

Transaction Summary
Install       2 Package(s)

Total download size: 489 k
Installed size: 2.5 M
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 489 k
Total                                                               3.3 MB/s | 489 kB     00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : 1:php-pear-1.9.4-4.el6.noarch                                                    1/2
  Installing : php-pecl-apc-3.1.9-2.el6.i686                                                    2/2
  Verifying  : 1:php-pear-1.9.4-4.el6.noarch                                                    1/2
  Verifying  : php-pecl-apc-3.1.9-2.el6.i686                                                    2/2

  php-pecl-apc.i686 0:3.1.9-2.el6

Dependency Installed:
  php-pear.noarch 1:1.9.4-4.el6


Step 2: Specify Shared Memory

Next, you’ll need to specify the size of the shared memory. To do this, open the apc.ini file:

[root@centos63 ~]# vi /etc/php.d/apc.ini

On line 12, specify the shared memory size:

; The size of each shared memory segment, with M/G suffix
; A "hint" about the number of distinct source files that will be included or
; requested on your web server. Set to zero or omit if you are not sure;

Step 3: Restart Apache

After specifying the shared memory size, you’ll need to restart Apache for the changes to take effect. Use the following command to restart Apache:

[root@centos63 ~]# /etc/rc.d/init.d/httpd restart
Stopping httpd:                                            [  OK  ]
Starting httpd:                                            [  OK  ]

Step 4: Verify APC Installation

Finally, to ensure that APC has been enabled, create a “phpinfo” file:

[root@centos63 ~]# vi /var/www/html/phpinfo.php

In this file, add the following lines:


After saving and closing the file, open it in a web browser. You should see APC listed among the enabled modules.

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Commands Mentioned

  • yum install php-pecl-apc -y – This command installs the APC extension on your server.
  • vi /etc/php.d/apc.ini – This command opens the APC configuration file where you can specify the shared memory size.
  • /etc/rc.d/init.d/httpd restart – This command restarts the Apache server, allowing the changes to take effect.
  • vi /var/www/html/phpinfo.php – This command creates a new PHP file where you can check if APC has been enabled.


Enabling APC with PHP on CentOS 6.3 can significantly enhance the performance of your PHP applications. This tutorial has guided you through the process of installing APC, specifying shared memory, restarting Apache, and verifying the APC installation.

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By following these steps, you can optimize your PHP environment and make your server more efficient.

By implementing APC, you’re taking a significant step towards optimizing your server and enhancing the performance of your PHP applications. If you have any further questions, refer to the FAQ section or feel free to ask.


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