installing CI4 via Composer, but getting error, please help!

I tried the composer command right above my project root to install CI4, but got this:

Code:

Could not find package codeigniter4/appstarter with stability stable in a version installable using your PHP version 7.0.33

I'm using PHP 7.3.+ and nowhere in my Plesk setup do I see anything about PHP 7.0.33.  I'm running Ubunto 16.04, Plesk 18, and Apache.  All my sites are using 7.3.

Please help!

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Okay, update, I got this with php -v in console:

Code:

PHP 7.0.33-0ubuntu0.16.04.7 (cli) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with the ionCube PHP Loader + ionCube24 v10.4.0, Copyright (c) 2002-2020, by ionCube Ltd.
    with Zend OPcache v7.0.33-0ubuntu0.16.04.7, Copyright (c) 1999-2017, by Zend Technologies

But my sites clearly use PHP 7.3+. Any ideas??