PHP支持断点续传，分块下载的类

<?php
 
/**
 * 支持断点下载的类
 */
class downloader {
 
    /**
     * download file to local path
     *
     * @param       $url
     * @param       $save_file
     * @param int   $speed
     * @param array $headers
     * @param int   $timeout
     * @return bool
     * @throws Exception
     */
    static function get($url, $save_file, $speed = 10240, $headers = array(), $timeout = 10) {
        $url_info = self::parse_url($url);
        if (!$url_info[&#39;host&#39;]) {
            throw new Exception(&#39;Url is Invalid&#39;);
        }
 
        // default header
        $def_headers = array(
            &#39;Accept&#39;          => &#39;*/*&#39;,
            &#39;User-Agent&#39;      => &#39;Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)&#39;,
            &#39;Accept-Encoding&#39; => &#39;gzip, deflate&#39;,
            &#39;Host&#39;            => $url_info[&#39;host&#39;],
            &#39;Connection&#39;      => &#39;Close&#39;,
            &#39;Accept-Language&#39; => &#39;zh-cn&#39;,
        );
 
        // merge heade
        $headers = array_merge($def_headers, $headers);
        // get content length
        $content_length = self::get_content_size($url_info[&#39;host&#39;], $url_info[&#39;port&#39;], $url_info[&#39;request&#39;], $headers, $timeout);
 
        // content length not exist
        if (!$content_length) {
            throw new Exception(&#39;Content-Length is Not Exists&#39;);
        }
        // get exists length
        $exists_length = is_file($save_file) ? filesize($save_file) : 0;
        // get tmp data file
        $data_file = $save_file . &#39;.data&#39;;
        // get tmp data
        $exists_data = is_file($data_file) ? json_decode(file_get_contents($data_file), 1) : array();
        // check file is valid
        if ($exists_length == $content_length) {
            $exists_data && @unlink($data_file);
            return true;
        }
        // check file is expire
        if ($exists_data[&#39;length&#39;] != $content_length || $exists_length > $content_length) {
            $exists_data = array(
                &#39;length&#39; => $content_length,
            );
        }
        // write exists data
        file_put_contents($data_file, json_encode($exists_data));
 
        try {
            $download_status = self::download_content($url_info[&#39;host&#39;], $url_info[&#39;port&#39;], $url_info[&#39;request&#39;], $save_file, $content_length, $exists_length, $speed, $headers, $timeout);
            if ($download_status) {
                @unlink($data_file);
            }
        } catch (Exception $e) {
            throw new Exception($e->getMessage());
        }
        return true;
    }
 
    /**
     * parse url
     *
     * @param $url
     * @return bool|mixed
     */
    static function parse_url($url) {
        $url_info = parse_url($url);
        if (!$url_info[&#39;host&#39;]) {
            return false;
        }
        $url_info[&#39;port&#39;]    = $url_info[&#39;port&#39;] ? $url_info[&#39;host&#39;] : 80;
        $url_info[&#39;request&#39;] = $url_info[&#39;path&#39;] . ($url_info[&#39;query&#39;] ? &#39;?&#39; . $url_info[&#39;query&#39;] : &#39;&#39;);
        return $url_info;
    }
 
    /**
     * download content by chunk
     *
     * @param $host
     * @param $port
     * @param $url_path
     * @param $headers
     * @param $timeout
     */
    static function download_content($host, $port, $url_path, $save_file, $content_length, $range_start, $speed, &$headers, $timeout) {
        $request = self::build_header(&#39;GET&#39;, $url_path, $headers, $range_start);
        $fsocket = @fsockopen($host, $port, $errno, $errstr, $timeout);
        stream_set_blocking($fsocket, TRUE);
        stream_set_timeout($fsocket, $timeout);
        fwrite($fsocket, $request);
        $status = stream_get_meta_data($fsocket);
        if ($status[&#39;timed_out&#39;]) {
            throw new Exception(&#39;Socket Connect Timeout&#39;);
        }
        $is_header_end = 0;
        $total_size    = $range_start;
        $file_fp       = fopen($save_file, &#39;a+&#39;);
        while (!feof($fsocket)) {
            if (!$is_header_end) {
                $line = @fgets($fsocket);
                if (in_array($line, array("\n", "\r\n"))) {
                    $is_header_end = 1;
                }
                continue;
            }
            $resp        = fread($fsocket, $speed);
            $read_length = strlen($resp);
            if ($resp === false || $content_length < $total_size + $read_length) {
                fclose($fsocket);
                fclose($file_fp);
                throw new Exception(&#39;Socket I/O Error Or File Was Changed&#39;);
            }
            $total_size += $read_length;
            fputs($file_fp, $resp);
            // check file end
            if ($content_length == $total_size) {
                break;
            }
            sleep(1);
            // for test
            //break;
        }
        fclose($fsocket);
        fclose($file_fp);
        return true;
 
    }
 
    /**
     * get content length
     *
     * @param $host
     * @param $port
     * @param $url_path
     * @param $headers
     * @param $timeout
     * @return int
     */
    static function get_content_size($host, $port, $url_path, &$headers, $timeout) {
        $request = self::build_header(&#39;HEAD&#39;, $url_path, $headers);
        $fsocket = @fsockopen($host, $port, $errno, $errstr, $timeout);
        stream_set_blocking($fsocket, TRUE);
        stream_set_timeout($fsocket, $timeout);
        fwrite($fsocket, $request);
        $status = stream_get_meta_data($fsocket);
        $length = 0;
        if ($status[&#39;timed_out&#39;]) {
            return 0;
        }
        while (!feof($fsocket)) {
            $line = @fgets($fsocket);
            if (in_array($line, array("\n", "\r\n"))) {
                break;
            }
            $line = strtolower($line);
            // get location
            if (substr($line, 0, 9) == &#39;location:&#39;) {
                $location = trim(substr($line, 9));
                $url_info = self::parse_url($location);
                if (!$url_info[&#39;host&#39;]) {
                    return 0;
                }
                fclose($fsocket);
                return self::get_content_size($url_info[&#39;host&#39;], $url_info[&#39;port&#39;], $url_info[&#39;request&#39;], $headers, $timeout);
            }
            // get content length
            if (strpos($line, &#39;content-length:&#39;) !== false) {
                list(, $length) = explode(&#39;content-length:&#39;, $line);
                $length = (int)trim($length);
            }
        }
        fclose($fsocket);
        return $length;
 
    }
 
    /**
     * build header for socket
     *
     * @param     $action
     * @param     $url_path
     * @param     $headers
     * @param int $range_start
     * @return string
     */
    static function build_header($action, $url_path, &$headers, $range_start = -1) {
        $out = $action . " {$url_path} HTTP/1.0\r\n";
        foreach ($headers as $hkey => $hval) {
            $out .= $hkey . &#39;: &#39; . $hval . "\r\n";
        }
        if ($range_start > -1) {
            $out .= "Accept-Ranges: bytes\r\n";
            $out .= "Range: bytes={$range_start}-\r\n";
        }
        $out .= "\r\n";
 
        return $out;
    }
}
 
 
#use age
/*
try {
    if (downloader::get(&#39;http://dzs.aqtxt.com/files/11/23636/201604230358308081.rar&#39;, &#39;test.rar&#39;)) {
        //todo
        echo &#39;Download Succ&#39;;
    }
} catch (Exception $e) {
    echo &#39;Download Failed&#39;;
}
*/
?>