The first thing you need to check is if your system has SSH2 features or not. You can simply check at phpinfo() in php function. If not, you can simply install SSH2 functions by below commands in root permission. The below case is based on Centos7.
# yum update # yum install make gcc libssh2 php-devel php-pear libssh2-devel
The next action you should do is installing ssh2 extension using pecl command for auto detect and download it once hit enter.
# pecl install -f ssh2
When you run above command, you may get the message like below
You should add "extension=ssh2.so" to php.ini
That means you should do it in order to make it work like below
https://www.thelinuxfaq.com/253-how-to-install-ssh2-extension-for-php-rhel-centos-7