How to work in the console with alternate versions of PHP

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