Pardon the long response ... but ...
You appear to be hosted with a provider that offers multiple versions of PHP ... some of which have reached end of life and probably shouldn't be used by any customer.
Running the cron script in 3.4.x code does require the higher version of PHP (7.0 ... which also has reached end of life). The docs at Moodle show how to setup cron on linux systems that are standalone ... ie, not the linux distro as built/modified by provider. Thus, the directions that show /usr/bin/php as the path actually is correct on most systems, on your providers system offering multple versions is in-correct.
So ... how to fix ...
From your ssh shell into your account, type: env [ENTER]
Look for a "PATH' line with variables/paths.
I can't share with you what that should look like on your system. Will say that showed me on a remotely hosted system with a provider that shall remain nameless ... right now ... that the customers environment found the php5 first and thus would not run any of the scripts in moodlecode/admin/cli/ which includes the cron.php script.
The following probably not yours but here's what it looked like on the system upon which I was working:
PATH=/usr/local/cpanel/3rdparty/lib/path-bin:/sbin:/bin:/usr/sbin:/usr/bin:/opt/cpanel/composer/bin
The command which php would show /usr/bin/php ... but that was NOT the php for CLI but for the web.
whereis php
if whereis available on your shell, showed other paths ... not included in the environment.
To set up the cron job on that system, had to use the path to the PHP version 7 cli ... which on that system happened to be in /usr/local/bin/
As a test, once you find the paths to the php executables:
Use the full path to php to see the version and which:
php -v on the system in the example here showed this:
PHP 7.1.26 (cgi-fcgi) (built: Jan 14 2019 19:44:52)
That's the PHP for the web ... see the (cgi-fcgi).
However, this one
/usr/local/bin/php -v shows
PHP 7.1.26 (cli) (built: Jan 14 2019 19:44:32) ( NTS )
see the 'cli' above.
So in the path to php in the setup of the cron job on the example system:
/usr/local/bin/php /full/path/to/moodle/code/admin/cli/cron.php
Then worked as expected.
All the scripts in moodlecode/admin/cli/ then all require the path to be:
/usr/local/bin/php ...
Hope that helps.
'spirit of sharing', Ken
