Follow these steps to install APC on a RHEL 5 server. 1. Install php-devel for phpize (if not installed). yum install php-devel 2. Install the apache devel pkgs for apxs (if needed). yum install httpd-devel 3. Make /tmp executable. mount -o remount,exec /tmp 4. Set the memory limit in /usr/share/pear/pearcmd.php to 16M. vi /usr/share/pear/pearcmd.php @ini_set('memory_limit', [...]