How to improve the access speed of PHP website through lazy loading?-PHP Tutorial-php.cn

How to improve the access speed of PHP website through lazy loading?

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Release： 2023-08-07 11:14:01

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How to improve the access speed of PHP website through lazy loading?

Lazy Loading is a common optimization technology that can improve website access speed, reduce unnecessary resource loading, and improve user experience. In PHP website development, lazy loading is usually used to delay loading of images, videos, scripts and other resources.

This article will introduce how to improve the access speed of PHP website through lazy loading, and demonstrate it through code examples.

Using lazy loading plug-in library

Lazy loading usually requires the help of plug-in library. Currently, there are many excellent lazy loading libraries to choose from, such as Lazy Load, Unveil.js, etc. These plug-in libraries can be introduced through npm or CDN, which is convenient and fast.

The following is a sample code that uses the Lazy Load plug-in library to implement lazy loading of images:

<!-- 在<head>标签中引入Lazy Load插件库 -->
<script src="https://cdn.jsdelivr.net/npm/lazyload/lazyload.js"></script>

<!-- 在<img>标签中添加"data-src"属性，将图片的真实地址放到"data-src"中，同时添加"class"属性指定懒加载样式-->
<img class="lazy" data-src="path/to/your/image.jpg" alt="">

<!-- 在<script>标签中初始化Lazy Load插件 -->
<script>
  document.addEventListener("DOMContentLoaded", function() {
    var lazyImages = [].slice.call(document.querySelectorAll("img.lazy"));

    if ("IntersectionObserver" in window) {
      let lazyImageObserver = new IntersectionObserver(function(entries, observer) {
        entries.forEach(function(entry) {
          if (entry.isIntersecting) {
            let lazyImage = entry.target;
            lazyImage.src = lazyImage.dataset.src;
            lazyImage.classList.remove("lazy");
            lazyImageObserver.unobserve(lazyImage);
          }
        });
      });

      lazyImages.forEach(function(lazyImage) {
        lazyImageObserver.observe(lazyImage);
      });
    }
  });
</script>

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In the above sample code, we added the <img> tag data-src attribute, and assign the real address of the image to data-src. At the same time, we also added the class attribute to specify the lazy loading style.

In the <script> tag, we first selected all images with the lazy class using the document.querySelectorAll method, and then used IntersectionObserver Monitor whether the image enters the window. When the image enters the window, we update the value of the src attribute, assign the real image address to src, and remove the lazy class to display the real picture. Finally, we call the observe method to start observing all lazy loading images.

Lazy loading of audio and video resources

In addition to pictures, lazy loading can also be used for audio and video resources. We can monitor the page scroll event to determine whether the audio and video elements are within the window, and load and play them when needed.

The following is a sample code that uses lazy loading to implement lazy loading of videos:

<video src="path/to/your/video.mp4" controls muted loop autoplay preload="none" id="lazy-video"></video>

<script>
  document.addEventListener("DOMContentLoaded", function() {
    var lazyVideo = document.getElementById("lazy-video");

    window.addEventListener("scroll", function() {
      var rect = lazyVideo.getBoundingClientRect();
      var inViewPort = (rect.top >= 0 && rect.bottom <= window.innerHeight);
      if (inViewPort) {
        lazyVideo.src = lazyVideo.dataset.src;
      }
    });
  });
</script>

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In the above sample code, we first added the <video> tag preload="none"Attribute to specify that the video is not automatically preloaded. Then, we listened to the page scroll event in the <script> tag and obtained the position information of the video element through the getBoundingClientRect method. Finally, we determine whether the video is within the window range. If so, assign the real video address to the src attribute to start loading and playing the video.

Through lazy loading technology, we can reduce the amount of resources when loading the initial page, thereby improving the access speed of the PHP website and providing a better user experience. I hope the lazy loading principle and sample code introduced in this article can be helpful to you.

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