PHP continues to maintain long connections, uses flush to continuously update the browser UI, and implements download progress bars.-PHP Tutorial-php.cn

PHP continues to maintain long connections, uses flush to continuously update the browser UI, and implements download progress bars.

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Release： 2016-08-08 09:31:05

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How to use PHP+JS to implement the upload progress bar? Most people may have implemented it, but what about downloading? How? The principle is similar, that is, reading and writing in batches, and how many bytes are read each time. However, the disadvantage of this is that the connection is long. Generally, the two solutions commonly used to implement the download progress bar are: one is to use a socket to maintain communication with the client. For communication, keep a long connection, use flush() to continuously update the browser UI, return the size of the downloaded data, and then display the download speed, progress bar, etc.; the second one is to interact with php and flash to display the progress bar.

<html>
<body>
<table border="1" width="300">
<tr><td width="100">文件大小</td><td width="200"><div id="filesize">未知长度</div></td></tr>
<tr><td>已经下载</td><td><div id="downloaded">0</div></td></tr>
<tr><td>完成进度</td><td><div id="progressbar" style="float:left;width:1px;text-align:center;color:#FFFFFF;background-color:#0066CC"></div><div id="progressText" style=" float:left">0%</div></td></tr>
</table>
<script type="text/javascript">
//文件长度
var filesize=0;
function $(obj) {return document.getElementById(obj);}

//设置文件长度
function setFileSize(fsize) {
    filesize=fsize;
    $("filesize").innerHTML=fsize;
}

//设置已经下载的,并计算百分比
function setDownloaded(fsize) {
    $("downloaded").innerHTML=fsize;
    if(filesize>0) {
        var percent=Math.round(fsize*100/filesize);
        $("progressbar").style.width=(percent+"%");
        if(percent>0) {
            $("progressbar").innerHTML=percent+"%";
            $("progressText").innerHTML="";
        } else {
            $("progressText").innerHTML=percent+"%";
        }
    }
}
</script>
<?php
ob_start();
@set_time_limit(300);//设置该页面最久执行时间为300秒
$url="http://dl_dir.qq.com/qqfile/qq/QQ2010/QQ2010Beta3.exe";//要下载的文件
$newfname="QQ2010Beta3.exe";//本地存放位置，也可以是E:\Temp\QQ2010Beta3.exe，这样做在Win7下要设置相应权限
$file = fopen ($url, "rb");
if ($file) {
    //获取文件大小
    $filesize = -1;
    $headers = get_headers($url, 1);
    if ((!array_key_exists("Content-Length", $headers))) $filesize=0;
    $filesize = $headers["Content-Length"];
    
    //不是所有的文件都会先返回大小的，有些动态页面不先返回总大小，这样就无法计算进度了
    if ($filesize != -1) {
        echo "<script>setFileSize($filesize);</script>";//在前台显示文件大小
    }
    $newf = fopen ($newfname, "wb");
    $downlen=0;
    if ($newf) {
        while(!feof($file)) {
            $data=fread($file, 1024 * 8 );//默认获取8K
            $downlen+=strlen($data);//累计已经下载的字节数
            fwrite($newf, $data, 1024 * 8 );
            echo "<script>setDownloaded($downlen);</script>";//在前台显示已经下载文件大小
            ob_flush();
            flush();
        }
    }
    if ($file) {
        fclose($file);
    }
    if ($newf) {
        fclose($newf);
    }
}
?>
</body>
</html>

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