Why doesn't PHP see the ssh2_connect() function?

Question

PHP

I'm trying to connect to sftp, the PHP manual says that you need to connect via ssh2_connect.
The script throws an error Call to undefined function ssh2_connect(). Can you please tell me how to connect the library, where is this function? In standard php, as I understand it, it is not. I used the instruction www.aplab.ru/log/148 , it did not help.
Thanks in advance to all who respond.

Answer 1

add ssh library to php
sudo apt install php-ssh2