用php自帶的curl功能實現的多線程下載工具，比file_get_contents，以及linux自帶的命令行curl、wget效率高多了，我親自測試過的。
大家如果覺得好，就拿去直接用吧。
/**
* @param mixed string or array，參數$urlArray是要抓取的網頁(或文件，下同)的網址，可以是單個網址，也可以是多個網址組成的數組。
*/
function multiDownload($urlArray) {
if (empty($urlArray)) return false;
$isStr = false;
if (is_string($urlArray)) {
$urlArray = array($urlArray);
$isStr = true;
}
self::log(sprintf("%s Multi thread download begin...", __METHOD__));
$mh = curl_multi_init(); //curl_multi_init -- Returns a new cURL multi handle
$curlArray = array();
foreach ($urlArray as $i => $url) {
self::log(sprintf("%s Download url: |%s|...", __METHOD__, $url));
$curlArray[$i] = curl_init($url);
curl_setopt($curlArray[$i], CURLOPT_RETURNTRANSFER, true); //設置爲true表示返回抓取的內容，而不是直接輸出到瀏覽器上。TRUE to return the transfer as a string of the return value of curl_exec() instead of outputting
it out directly
curl_setopt($curlArray[$i], CURLOPT_AUTOREFERER, true); //自動設置referer。TRUE to automatically set the Referer: field in requests where it follows a Location: redirect.
curl_setopt($curlArray[$i], CURLOPT_FOLLOWLOCATION, true); //跟蹤url的跳轉，比如301, 302等
curl_setopt($curlArray[$i], CURLOPT_MAXREDIRS, 2); //跟蹤最大的跳轉次數
curl_setopt($curlArray[$i], CURLOPT_HEADER, 0); //TRUE to include the header in the output.
curl_setopt($curlArray[$i], CURLOPT_ENCODING, ""); //接受的編碼類型,The contents of the "Accept-Encoding: " header. This enables decoding of the response. Supported encodings are "identity",
"deflate", and "gzip". If an empty string, "", is set, a header containing all supported encoding types is sent.
curl_setopt($curlArray[$i], CURLOPT_CONNECTTIMEOUT, 5); //連接超時時間
curl_multi_add_handle($mh, $curlArray[$i]); //curl_multi_add_handle -- Add a normal cURL handle to a cURL multi handle
}
$running = NULL;
$count = 0;
do {
//10秒鐘沒退出，就超時退出
if ($count++>100) break;
usleep(100000);
curl_multi_exec($mh, $running); //curl_multi_exec -- Run the sub-connections of the current cURL handle
} while($running > 0);
$content = array();
foreach ($urlArray as $i => $url) {
$content[$url] = curl_multi_getcontent($curlArray[$i]); //curl_multi_getcontent -- Return the content of a cURL handle if CURLOPT_RETURNTRANSFER is set
}
//curl_multi_remove_handle -- Remove a multi handle from a set of cURL handles
foreach ($urlArray as $i => $url){
curl_multi_remove_handle($mh, $curlArray[$i]);
}
//curl_multi_close -- Close a set of cURL handles
curl_multi_close($mh);
self::log(sprintf("%s Multi thread download end...", __METHOD__));
//如果參數$urlArray是字符串，則將返回值也轉換爲字符串
if ($isStr) $content = implode('', $content);
return $content;
}