The Magento2 Command Line Interface (CLI) needs to use the same version of PHP as your local web environment. You can check this by setting up an info.php script with in it “<?php phpinfo();” and comparing the output with the command “$ which php“.
You may find you are running two different versions of PHP each with its own PHP executable: by default one will be located in /usr/bin and another in somewhere like /opt/lampp/bin.
If you want to execute /opt/lampp/bin/php instead of /usr/bin, open your .bashrc file
sudo nano ~/.bashrc
At the very end add a new line:
PATH=/opt/lampp/bin:$PATH
Once you have saved .bashrc, run the command:
source .bashrc
You will now find bash is running the same PHP version and environment as your web server