提供的一个好用放大镜插件，基于juqery，非原创。

(function(e){var i={shadecolor:"#FFD24D",shadeborder:"#FF8000",shadeopacity:.5,cursor:"move",layerwidth:400,layerheight:300,layerborder:"#DDD",fade:true,largewidth:1280,largeheight:960};var t=function(t){t=e.extend({},i,t);e(this).each(function(){var i=e(this).css("position","relative");var h=i.children().first();var r={x:h.width()/t.largewidth,y:h.height()/t.largeheight};var o={shade:{width:t.layerwidth*r.x-2,height:t.layerheight*r.y-2}};var a=e("<div>").css({position:"absolute",left:"0px",top:"0px","background-color":t.shadecolor,border:"1px solid "+t.shadeborder,width:o.shade.width,height:o.shade.height,opacity:t.shadeopacity,cursor:t.cursor});a.hide().appendTo(i);var d=e("<img>").css({position:"absolute",display:"block",width:t.largewidth,height:t.largeheight});var s=e("<div>").css({position:"absolute",left:i.width()+5,top:0,"background-color":"#111",overflow:"hidden",width:t.layerwidth,height:t.layerheight,border:"1px solid "+t.layerborder});d.attr("src",i.attr("href"));d.appendTo(s);s.hide().appendTo(i);var n={x:o.shade.width/2,y:o.shade.height/2};var l={width:i.innerWidth()-a.outerWidth(),height:i.innerHeight()-a.outerHeight()};var g=function(){a.show();if(t.fade)s.stop().fadeIn(300);else s.show()};var c=function(){a.hide();s.hide()};var f=i.offset();i.mousemove(function(e){var t=e.pageX-f.left;var h=e.pageY-f.top;if(t<0||t>i.innerWidth())return c();if(h<0||h>i.innerHeight())return c();t=t-n.x;h=h-n.y;if(t<0)t=0;if(h<0)h=0;if(t>l.width)t=l.width;if(h>l.height)h=l.height;a.css({left:t,top:h});d.css({left:0-t/r.x,top:0-h/r.y})}).mouseenter(g).mouseleave(c)})};e.fn.extend({enlarge:t})})(jQuery);

调用上面的插件   

 $(function(){
      $("#demo").enlarge({ 
         // 鼠标遮罩层样式 
         shadecolor: "#FFD24D", 
         shadeborder: "#FF8000", 
         shadeopacity: 0.4, 
         cursor: "move", 


         // 大图外层样式 
         layerwidth: 480, 
         layerheight: 360, 
         layerborder: "#DDD", 
         fade: true, 


         // 大图尺寸 
         largewidth: 960, 
         largeheight: 720 
        });
     }); 

html中代码：

<a href="../upload/{$data['img']}" id="demo" style="position: relative;float: left; z-index:999;">
              <img src="../upload/{$data['img']}">
    </a>

一个放大镜就做好啦，