After connecting to the server via SSH, you can find out what alternate versions of PHP are installed via the command

whereis php  
php: /usr/bin/php /usr/share/php /opt/php71/bin/php  

From this output, you can see that there is a main version of PHP (/usr/bin/php) and an alternate version PHP 7.1 (/opt/php71/bin/php).
You can work with the alternate by specifying the full path to the interpreter in the console. For example:

/opt/php71/bin/php -v
PHP 7.1.13 (cli) (built: Jan 19, 2018 12:16:19) ( NTS )  
Copyright (c) 1997-2017 The PHP Group  
Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies