安利兩種php的下載函數(shù)

1.readfile,獲取文件的句柄(注意:這里是句柄而不是文件,所以只占用很小的內(nèi)存)并將句柄輸出到緩沖區(qū)

function readfile_download($url, $filename,$opt = null)
{
    //設(shè)置http下載消息報(bào)文
    header("Content-Disposition:  attachment;  filename=" . $filename);
    header("Pragma:  no-cache");
    header("Expires:  0");
    //有些下載需要附帶cookie和useragent
    $cookie = $opt['cookie'] ? $opt['cookie'] : '';
    $useragent = $opt['useragent'] ? $opt['useragent'] : '';
    $opts = array(
        'http' => array(
            'method' => 'GET',
            'header' =>
                "UserAgent:$useragent\r\n" .
                "Cookie:$cookie \r\n",
        )
    );
    $context = stream_context_create($opts);
    readfile($url,false,$context);
}

但是緩沖區(qū)同樣有限制大小,默認(rèn)的緩沖區(qū)只有4k,一旦緩沖區(qū)溢出,同樣也會(huì)占用內(nèi)存,所以如果要進(jìn)行多人大文件下載,緩沖區(qū)也要被限制

2.使用fopen獲取遠(yuǎn)程文件的句柄,然后使用fread分段獲取并輸出,這樣不僅占用的內(nèi)存少,而且占據(jù)的緩沖區(qū)也少,可以用于多人大文件下載場(chǎng)景

function0 fopen_download($url, $filename,$opt = null,$limit = 1024)
{
    //設(shè)置http下載消息報(bào)文
    header("Content-Disposition:  attachment;  filename=" . $filename);
    header("Pragma:  no-cache");
    header("Expires:  0");
    //有些下載需要附帶cookie和useragent
    $cookie = $opt['cookie'] ? $opt['cookie'] : '';
    $useragent = $opt['useragent'] ? $opt['useragent'] : '';
    $opts = array(
        'http' => array(
            'method' => 'GET',
            'header' =>
                "UserAgent:$useragent\r\n" .
                "Cookie:$cookie \r\n",
        )
    );
    $context = stream_context_create($opts);
    $handle = fopen($url, "r", false, $context);
    //輸出
    while (!feof($handle)) {
        $content = fread($handle, intval($limit));
        echo $content;
        ob_flush();
    }
}

3.有些考慮到安全的項(xiàng)目,是會(huì)禁用fopen打開URL,又或是考慮到打開URL的穩(wěn)定性和性能,所以想使用cURL函數(shù)

function download($url,$filename,$opt=null,$limit = 1024)
{
    //curl獲取遠(yuǎn)程文件并儲(chǔ)存在臨時(shí)文件內(nèi)
    $ch = curl_init();
    $fp = tmpfile();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_FILE, $fp);
    $cookie = $opt['cookie'] ? $opt['cookie'] : null;
    $useragent = $opt['useragent'] ? $opt['useragent'] : $_SERVER['HTTP_USER_AGENT'];
    curl_setopt($ch, CURLOPT_COOKIE, $cookie);
    curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
    curl_exec($ch);
    curl_close ($ch);
    //設(shè)置http下載消息報(bào)文
    header("Content-Disposition:  attachment;  filename=" . $filename);
    header("Pragma:  no-cache");
    header("Expires:  0");
    rewind($fp);
    //輸出
    while (!feof($fp) && is_resource($fp)) {
        $content = fread($fp, $limit);
        echo $content;
        ob_flush();
    }
    //關(guān)閉并銷毀臨時(shí)文件
    fclose($fp);
}