~$ sudo apt-get

First, mount the /tmp partition with exec permissions.

mount -o remount,exec /tmp

To install a package via pecl, run the following.

pecl install ssh2
(If the package is in a state other than stable, append the state after the package name ‘pecl install ssh2-beta’)

Last few lines of the module install will list the location of the library, usually /usr/lib/php/modules. Create a ini file with the module name within /etc/php.d/ with the extension directive.

# cat /etc/php.d/gd.ini
; Enable gd extension module
extension=gd.so

At this point, run the mount command to reestablish noexec for the /tmp partition.

mount -o remount,noexec /tmp

Gracefully restart apache and you are done.