这篇文章主要为大家详细介绍了php实现文件预览功能，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
上一篇博客是上传功能，本篇是上传后图片预览和更改：
代码如下：
1.yulan.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
#yl{ width:200px; height:300px; background-image:url(images/timg1.jpg); background-size:200px 300px;}
#file{ width:200px; height:300px; float:left; opacity:0;}
</style>
</head>
<body>
<form id="sc" action="ylchuli.php" method="post" enctype="multipart/form-data" target="shangchuan">
<input type="hidden" name="tp" value="" id="tp" />
<p id="yl">
<input type="file" name="file" id="file" onchange="document.getElementById('sc').submit()" />
</p>
</form>
<iframe style="display:none" name="shangchuan" id="shangchuan">
</iframe>
</body>
<script type="text/javascript">
//回调函数,调用该方法传一个文件路径，改变背景图
function showimg(url)
{
var p = document.getElementById("yl");
p.style.backgroundImage = "url("+url+")";
document.getElementById("tp").value = url;
}
</script>
</html>2.ylchuli.php
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<?php
if($_FILES["file"]["error"])
{
echo $_FILES["file"]["error"];
}
else
{
if(($_FILES["file"]["type"]=="image/jpeg" || $_FILES["file"]["type"]=="image/png")&& $_FILES["file"]["size"]<1024000)
{
$fname = "./images/".date("YmdHis").$_FILES["file"]["name"];
$filename = iconv("UTF-8","gb2312",$fname);
if(file_exists($filename))
{
echo "<script>alert('该文件已存在！');</script>";
}
else
{
move_uploaded_file($_FILES["file"]["tmp_name"],$filename);
$delurl = iconv("UTF-8","gb2312",$_POST["tp"]);
unlink($delurl); //删除文件
echo "<script>parent.showimg('{$fname}');</script>";
}
}
} 
