How to prevent those PHP variables from being cached on WordPress?

Question

I'm using this code in functions.php on WordPress to generate an affiliate link based on the visitor location, It's working perfectly but the problem is that if page caching is turned on (W3 Total Cache), The variables get cached so if someone from the UK was the first one to open the page then the second one from Germany opened the page he will get the same link that the first visitor got.

One more thing please, I'm still very new to PHP and javascript so I would appreciate if the answer was simplified enough

 <?php

add_action( 'woocommerce_before_add_to_cart_button', 'affiliate_link', 10);

function affiliate_link() { 
$not_avilable_country = '<div id="amz_not_avilable" class="amz_not_avilable">This product is not avilable in your country yet</div>';


// IP Geolocation   
$country_code = $_SERVER ["HTTP_CF_IPCOUNTRY"];
// Get Custom Fields
$de_asin = get_post_meta(get_post()->ID, "wccaf_de_asin", true );
$uk_asin = get_post_meta(get_post()->ID, "wccaf_uk_asin", true );



//////////////////////////////////////////////


if ($country_code=="DE" or $country_code=="DE") {
    $amazon_domain = 'https://www.amazon.de';
 // $associate_id = 'bonstato-21';
    $asin = $de_asin;
}

else if ($country_code=="GB" && $uk_asin!=="") {
    $amazon_domain = 'https://www.amazon.co.uk';
 // $associate_id = 'bonmedico-21';
    $asin = $uk_asin;
}


///////////////////////////////////////////////

        if( wp_is_mobile() ) {

// Amazon Link For Mobile       
?>
<script>
    function amzGo(){
                window.location='<?php echo $amazon_domain ?>/dp/<?php echo $asin ?>/?tag=<?php echo $associate_id ?>';
  }
</script>
<?php
        }

else {

// Amazon Link For PC
    ?>
<script>
    function amzGo(){
        window.location='<?php echo $amazon_domain ?>/gp/aws/cart/add.html?AssociateTag=<?php echo $associate_id ?>&ASIN.1=<?php echo $asin ?>&Quantity.1=1';
  }
</script>
<?php
}


?>
     <div class="buy_amz_btn_wrap" >  
<button type="button" id="buy_amz_btn" class="buy_amz_btn" onclick="amzGo();"><i class="fa fa-amazon fa-amz"></i><?php echo $amz_btn_title ?></button>                           
</div>
    <?php

}

?>

Answer 1

Page caching generates a static HTML version of the page so IP geolocation occurs on the first rendering and is not triggered on subsequent renderings - your use case is not compatible with W3 Total Cache's page caching.

It's possible to accomplish what you are trying to accomplish with page caching, however, you would need to write your own caching implementation to check against a visitor geolocation cookie or $_GET parameter to serve different static HTML documents dependent upon the contents of its value (well beyond the scope of any simple coding).