Installing this module for use with CentOS 5.?? or 6.?
1. Install your favorite PHP RPM packages. Make sure that one of your favorite packages is pear, so pecl gets installed in-tow.
2. Find and install *RPMS* of libssh2 of a version >= 1.2, get both the base lib package (libssh2-1.2.*.rpm) and the devel package that includes headers (libssh2-devel-1.2.*.rpm) of the EXACT SAME VERSION. Finding these packages took a few minutes of googling, and I invite an editor that has a trusted source for these to attach URLs as appropriate. (Yes, the version below is ancient)
# rpm -ivh libssh2-1.2.6-1.el5.rf.x86_64.rpm libssh2-devel-1.2.6-1.el5.rf.x86_64.rpm
3. Install the PHP module via pecl
# pecl install ssh2-0.12
4. Make PHP see the newly-installed extension
# echo "extension=ssh2.so" > /etc/php.d/ssh2.ini
5. Restart apache