Use different PHP version CLI executable for one command
Default PHP executable can be found using:
$ which php
In most cases it is link to particular PHP version:
lrwxrwxrwx 1 root root 21 aug 15 2016 /usr/bin/php -> /usr/bin/php7.1
To change it to different version just relink it to another
$ sudo rm /usr/bin/php
$ sudo ln -s /usr/bin/php5.6 /usr/bin/php
Before relink you have to make sure target PHP version is installed.
Maybe you can try to fix the environnement!
$ php -v
PHP 5.4.x (cli) ...
$ set PATH="/usr/lib64/php5.6/bin:$PATH"
$ php -v
PHP 5.6.x (cli) ...
Or, if you don't want to modify the PATH for your shell session, you can scope the change for the current command only:
$ php -v
PHP 5.4.x (cli) ...
$ env PATH="/usr/lib64/php5.6/bin:$PATH" php -v
PHP 5.6.x (cli) ...
$ php -v
PHP 5.4.x (cli) ...