See https://joshuatz.com/posts/2019/excluding-employee-traffic-from-google-analytics-pixels-and-more

PHP_Conditional_Tag_By_IP.php

<!-- Use this to set the list of IP addresses you DONT want your tags loading for -->
<?php $blockTagsFor = array('216.3.128.12','19.117.63.126','2001:0db8:85a3:0000:0000:8a2e:0370:7334'); ?>

<?php if (in_array($_SERVER['REMOTE_ADDR'],$blockTagsFor,false)==false): ?>
    <!-- Put all the tags you want to conditionally load here. GA example below: -->


    <!-- Global Site Tag (gtag.js) - Google Analytics -->
    <script async src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"></script>
    <script>
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());

    gtag('config', 'GA_MEASUREMENT_ID');
    </script>

<?php endif; ?>