Install PECL SSH2 extension for PHP

$ sudo pecl channel-update pecl.php.net
$ sudo apt-get install libssh2-1-dev
$ sudo pecl install -a ssh2-0.12
$ echo 'extension=ssh2.so' | sudo tee /etc/php5/mods-available/ssh2.ini > /dev/null
$ sudo php5enmod ssh2

Installing libssh2 via tar.gz from http://sourceforge.net/projects/libssh2/ help a lot (--with-ssh2=/usr/local/include/).

But :

yum install libssh2-devel

...is a better idea.