tp3.2验证码刷新只需加onclick，即可实现点击换一张
<div class="form-group"> <input type="text" style="width:120px; height:40px; float:left;"placeholder="验证码" name="yzm" maxlength="4" class="form-control"> <img style="cursor:pointer; width:200px; height:40px; " src="__APP__/Tpl/Login/yzm" alt="点击更换" onClick="this.src=this.src+'?'+Math.random();"/> </div>
