php 下载文件的函数

PHP文件下载，PHP本身不会下载文件，实质是通过告诉浏览器要下载文件，要下载的文件在哪？

PHP函数下载
下载一：

header("content-disposition:attachment;filename=$file_name");//告诉浏览器下载文件名称类型
header("content-length:".filesize($file));//文件大小
@readfile($file);//读取文件并写入到输出缓冲

下载二：

header("Content-type:application/octet-stream");
header("Accept-Ranges:bytes");
header("Content-Type:application/force-download");
header("Content-Disposition:inline;filename=".$filename);
header("Accept-Length:".filesize($File));
@readfile($File);//读取文件并写入到输出缓冲

下载三：php断点续传

function download($url, $filename) {
    // 获得文件大小, 防止超过2G的文件, 用sprintf来读
    $filesize = sprintf ( "%u", filesize ( $url ) );
    if (! $filesize) {
        return;
    }
    header ( "Content-type:application/octet-stream
" ); //application/octet-stream
    header ( "Content-type:unknown/unknown;" );
    header ( "Content-disposition: attachment; filename="" . $filename . """ );
    header ( "Content-transfer-encoding: binary" );
    if ($range = getenv ( "HTTP_RANGE" )) { // 当有偏移量的时候，采用206的断点续传头
        $range = explode ( "=", $range );
        $range = $range [1];
        header ( "HTTP/1.1 206 Partial Content" );
        header ( "Date: " . gmdate ( "D, d M Y H:i:s" ) . " GMT" );
        header ( "Last-Modified: " . gmdate ( "D, d M Y H:i:s", filemtime ( $url ) ) . " GMT" );
        header ( "Accept-Ranges: bytes" );
        header ( "Content-Length:" . ($filesize - $range) );
        header ( "Content-Range: bytes " . $range . ($filesize - 1) . "/" . $filesize );
        header ( "Connection: close" . "

" );
    } else {
        header ( "Content-Length:" . $filesize . "

" );
        $range = 0;
    }
    loadFile ( $url );
}

function loadFile($filename, $retbytes = true) {
    $buffer = "";
    $cnt = 0;
    $handle = fopen ( $filename, "rb" );
    if ($handle === false) {
        return false;
    }
    while ( ! feof ( $handle ) ) {
        $buffer = fread ( $handle, 1024 * 1024 );
        echo $buffer;
        ob_flush ();
        flush ();
        if ($retbytes) {
            $cnt += strlen ( $buffer );
        }
    }
    $status = fclose ( $handle );
    if ($retbytes && $status) {
        return $cnt; // 返回从文件中读入的字节数，像readfile()。
    }
    return $status;
}

//输入2个参数即可完成下载
download($url, $filename)

以上就介绍了php 下载文件的函数