php 下载文件的函数，

php 下载文件的函数，

通过函数完成下载文件的PHP功能代码

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\n" ); //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" . "\n\n" );
    } else {
        header ( "Content-Length:" . $filesize . "\n\n" );
        $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; // return num. bytes delivered like readfile() does.
    }
    return $status;
}
输入2个参数即可完成下载

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download($url, $filename)

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