How to include CF GeopPlugin in PHP?

<?php echo do_shortcode('[cf_geo return="city"]'); ?>

or directly using PHP class:

<?php
if(class_exists("CF_Geoplugin")){
    // include plugin class
     $cf_geo = new CF_Geoplugin;
     // get data
     $geo = $cf_geo->get();
     // print data
     echo $geo->city;
}
?>

You are free to decide what method is best for you to use.

Later you can use data like:

<?php
$country = strtoupper($geo->country_code);
if(in_array($country, ['US','UK']) !== false)
    echo 'Hello World';
else if(in_array($country, ['DE','GB']) !== false)
    echo 'Hallo Wereld';
else
    echo 'Hakuna Matata';
?>