* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    body {
      background: #352323 url(images/a.png);
    }
    img {
      display: block;
    }
    section {
      max-width: 95%;
      margin: 0 auto;
      overflow: hidden;
      column-count: 5;
      column-gap: 0;
      column-fill: auto;
    }
    figure {
      border: 2px solid pink;
      margin: 0 5px 10px;
      break-inside: avoid;
      padding: 5px;
    }
    figure img {
      width: 100%;
    }
    figcaption {
      padding: 10px 0;
      text-align: center;
      font-weight: 900;
      color: #a77869;
    }

 <section>
    <!-- <figure>
      <img src="images/1.jpg" >
      <figcaption>往后余生，風(fēng)雪是你</figcaption>
    </figure> -->
</section>

window.onload = function() {
    var section = document.getElementsByTagName('section')[0];
    //運(yùn)行ajax函數(shù)；
    ajax('get', 'active.php', 'num=10', function(data) {
      //解析json對(duì)象
      let img_data = JSON.parse(data);
      console.log(img_data);
      //循環(huán)建多少圖片配多少標(biāo)簽
      for (let i = 0; i < img_data.length; i++) {
        //建立figure標(biāo)簽
        let figure = document.createElement('figure');
        //創(chuàng)建兩個(gè)子元素img和figcaption，并賦值
        let img = document.createElement('img');
        img.src = img_data[i];
        let figcaption = document.createElement('figcaption');
        figcaption.innerHTML = '往后余生，風(fēng)雪是你';
        //插節(jié)點(diǎn)
        figure.appendChild(img);
        figure.appendChild(figcaption);
        section.appendChild(figure);
      }
    });
    document.onscroll = function() {
      var scrollTop = document.documentElement.scrollTop; //距離網(wǎng)頁(yè)高度
      console.log(scrollTop);
      // var ks = document.documentElement.clientHeight; //可是化窗口高度
      var ks = window.innerHeight || document.documentElement.clientHeight; //可是化窗口高度/兼容方法
      var ht = document.documentElement.offsetHeight; //html總高度
      // console.log(ht);
      if (scrollTop + 1 >= ht - ks) { //鼠標(biāo)滾動(dòng)的距離大于html總高度-窗口的距離(也就是html在可視窗口之下的總高度)時(shí) 觸發(fā)函數(shù);
        //執(zhí)行函數(shù)
        ajax('get', 'active.php', 'num=10', function(data) {
          //解析json對(duì)象
          let img_data = JSON.parse(data);
          console.log(img_data);
          //循環(huán)建多少圖片配多少標(biāo)簽
          for (let i = 0; i < img_data.length; i++) {
            //建立figure標(biāo)簽
            let figure = document.createElement('figure');
            //創(chuàng)建兩個(gè)子元素img和figcaption，并賦值
            let img = document.createElement('img');
            img.src = img_data[i];
            let figcaption = document.createElement('figcaption');
            figcaption.innerHTML = '往后余生，風(fēng)雪是你';
            //插節(jié)點(diǎn)
            figure.appendChild(img);
            figure.appendChild(figcaption);
            section.appendChild(figure);
          }
        });
      }
    }
  };

/**
 * ajax封裝
 * @param {string} mehod請(qǐng)求數(shù)據(jù)方法
 * @param {string} url 請(qǐng)求地址
 * @param {string} data 請(qǐng)求參數(shù)
 * @param {[functiong]} success [請(qǐng)求成功之后執(zhí)行的函數(shù)0]
 * @return {[none]} none
 */
function ajax(mehod, url, data, success) {
  var xhr = null;
  if (window.XMLHttpRequest) {
    xhr = new XMLHttpRequest();
  } else {
    xhr = new ActiveXObject("Microsoft.xmlhttp")
  }
  //如果有參數(shù)get方法需要拼接字符串url+?+data
  if (mehod === 'get' && data) {
    url += '?' + data;
  }
  //open方法
  xhr.open(mehod, url, true);
  //send方法
  if (mehod === 'get') {
    xhr.send();
  } else {
    xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded');
    xhr(data);
  }
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      success && success(xhr.responseText);
    }
  }

<?php 
header("Content-type:text/html;charset=utf-8");
$num = $_GET['num']; // api調(diào)用者傳遞的需要的圖片頁(yè)數(shù) 
$img = file("img.txt");
// var_dump($img);
$array_url = array();
for($i=0;$i<$num;$i++){
  $url = array_rand($img);
  array_push($array_url,$img[$url]);
}
$a = json_encode($array_url);
echo $a;