lazy-load-wistia.php

<?php $video_id = 'the video id'; ?>

<div id="wistia_<?= $video_id; ?>" class="wistia_embed_api wistia_async_<?= $video_id; ?> popover=false wistia_embed_wrapper" data-video="<?= $video_id; ?>"></div>

wistia.js

//  ========================
//  Wistia injection scripts
//  =========================

function doWistia(wistiaId, wistiaType) {
    var baseUrl = "https://fast.wistia.com/oembed/?url=";
    var accountUrl = encodeURIComponent("https://home.wistia.com/medias/");

    var xhr = new XMLHttpRequest();
        
    xhr.open('GET', baseUrl + accountUrl + wistiaId + "&format=json&callback=?");
    xhr.send(null);
    xhr.onreadystatechange = function() {
        var DONE = 4; 
        var OK = 200;
        if (xhr.readyState === DONE && xhr.status === OK) {
            switch (wistiaType) {
                case "popover":
                    wistiaEmbed = Wistia.embed(wistiaId, {
                        autoPlay: true,
                        controlsVisibleOnLoad: false,
                        popover: true,
                        popoverAnimateThumbnail: true,
                        videoFoam: true,
                        videoWrapper: 'wistia_embed_popover',
                    });
                break;

                case "inline":
                    wistiaEmbed = Wistia.embed(wistiaId, {
                        autoPlay: false,
                        controlsVisibleOnLoad: false,
                        videoFoam: true,
                        videoWrapper: 'wistia_embed_api',
                    });
                break;
            }
        } else {
            return;
        }
    };
};

function setupWistia(e) {

    if (document.querySelector('.wistia_embed_popover')) {
        wistiaId = document.querySelector('.wistia_embed_popover').getAttribute('data-wistia-id');
        wistiaType = 'popover';
    }

    if (document.querySelector('.wistia_embed_api')) {
        wistiaId = document.querySelector('.wistia_embed_api').getAttribute('data-video');
        wistiaType = 'inline';
    }

    //  inject wistia script (If needed)
    if (typeof wistiaId !== 'undefined') {
        var d = document;
        script = d.createElement('script');
        script.type = 'text/javascript';
        script.async = true;
        script.src = 'https://fast.wistia.com/assets/external/E-v1.js';
        d.getElementsByTagName('html')[0].appendChild(script);

        script.onload = function() {
            doWistia(wistiaId, wistiaType);
        };
    } else {
        return;
    }
};

window.addEventListener("load", pageFullyLoaded, false);

function pageFullyLoaded(e) {
    setupWistia(e);
};