上传文件后获得返回的信息

<form id="tj_1" action="public/sccl.php" target="hidden_frame" method="post" enctype="multipart/form-data">
        
        <input type='text' hidden="hidden" id="tj_aa" name="tj_aa"/>
        
        <div id="tj_pic" style=" position:relative; border-radius:5px; left:350px; top:-120px; 200px; height:200px;  background:url(img/1.jpg) no-repeat; background-size:100% 100%;">
            <input type="file" name="file" style=" 200px; height:200px; margin-bottom:20px; opacity:0;" onchange="document.getElementById('tj_1').submit()"/><div style="200px; text-align:center">选择商品图片</div>
            <img id="pic" style="display:none"/>
        </div>
    </form>
    <iframe style="display:none;" name="hidden_frame" id="hidden_frame">
    </iframe>

echo "<script language='javascript'>parent.showimg('"."pic/" . $_FILES["file"]["name"]."')</script>";

function showimg(aa)
{
    var l = document.getElementById("tj_pic");
    var p = document.getElementById("pic");
    
    l.style.backgroundImage = "url("+aa+")";
    p.setAttribute("src",aa);
}