Detailed explanation of PHP imitation WeChat multiple image preview and upload examples

<ul id="ul_pics" class="ul_pics clearfix"> 
 <li><img src="logo.png" id="btn" class="img_common" /></li> 
</ul>

var uploader = new plupload.Uploader({//创建实例的构造方法 
 runtimes: 'html5,flash,silverlight,html4', //上传插件初始化选用那种方式的优先级顺序 
 browse_button: 'btn', // 上传按钮 
 url: "ajax.php", //远程上传地址 
 flash_swf_url: 'plupload/Moxie.swf', //flash文件地址 
 silverlight_xap_url: 'plupload/Moxie.xap', //silverlight文件地址 
 filters: { 
  max_file_size: '10mb', //最大上传文件大小（格式100b, 10kb, 10mb, 1gb） 
  mime_types: [//允许文件上传类型 
   {title: "files", extensions: "jpg,png,gif,jpeg"} 
  ] 
 }, 
 multi_selection: true, //true:ctrl多文件上传, false 单文件上传 
 init: { 
  FilesAdded: function(up, files) { //文件上传前 
   if ($("#ul_pics").children("li").length > 30) { 
    alert("您上传的图片太多了！"); 
    uploader.destroy(); 
   } else { 
    var li = ''; 
    plupload.each(files, function(file) { //遍历文件 
     li += "<li id=&#39;" + file[&#39;id&#39;] + "&#39;><p class=&#39;progress&#39;><span class=&#39;bar&#39;></span><span class=&#39;percent&#39;>0%</span></p></li>"; 
    }); 
    $("#ul_pics").prepend(li); 
    uploader.start(); 
   } 
  }, 
  UploadProgress: function(up, file) { //上传中，显示进度条 
   var percent = file.percent; 
   $("#" + file.id).find(&#39;.bar&#39;).css({"width": percent + "%"}); 
   $("#" + file.id).find(".percent").text(percent + "%"); 
  }, 
  FileUploaded: function(up, file, info) { //文件上传成功的时候触发 
   var data = eval("(" + info.response + ")");//解析返回的json数据 
   $("#" + file.id).html("<input type=&#39;hidden&#39;name=&#39;pic[]&#39; value=&#39;" + data.pic + "&#39;/><input type=&#39;hidden&#39;name=&#39;pic_name[]&#39; value=&#39;" + data.name + "&#39;/><img class=&#39;img_common&#39; onclick=delPic(&#39;" + data.pic + "&#39;,&#39;" + file.id + "&#39;) src=&#39;" + data.pic + "&#39;/>");//追加图片 
  }, 
  Error: function(up, err) { //上传出错的时候触发 
   alert(err.message); 
  } 
 } 
}); 
uploader.init();

function delPic(pic, file_id) { //删除图片 参数1图片路径 参数2 随机数 
 if (confirm("确定要删除吗？")) { 
  $.post("del.php", {pic: pic}, function(data) { 
   $("#" + file_id).remove() 
  }) 
 } 
}