/**

 * 下载远程图片到本地

 *

 * @param string $txt 用户输入的文字，可能包含有图片的url

 * @param string $keywords  网站域名关键字，路径中含有这个关键字的图片(即本网站图片)跳过

 * @return string

 */

public function getImageToLocal($txt,$keywords = 'xxx.com')

{

    $matches = array();

    preg_match_all('/<img.+?src=(.+?)\s/is',$txt,$matches);

    if(!is_array($matches)) return $txt;

    $curl = new curl();

    $curl -> setHeader(true);

    foreach ($matches[1] as $k => $v)

    {

        $url = trim($v,"\"'");

        $ext = '';

        if(strpos($url,$keywords) === false && substr($url,0,7) == 'http://') //非本站地址,需要下载图片

        {

            $curl -> setUrl($url);

            $curl -> setTimeout(5);

            $data = $curl -> send();

            list($header,$imageData) = explode("\n\n",$data);

            if($ext = $this -> getImageExtension($header))

            {

                    $file = IMAGE_SAVE_DIR . date('YmdHis') . rand(1,100) . $k . '.' . $ext;

                    @file_put_contents($file,$imageData);

                    if(is_file($file)) $txt = str_replace($v,'"' . str_replace(ROOT,'',$file) . '"',$txt);

            }

        }

    }

    return $txt;

}

/**

 * 从HTTP头分离出图片的扩展名

 *

 * @param string $header HTTP头

 * @return string

 */

function getImageExtension($header)

{

    $arr = explode("\n",$header);

    foreach($arr as $k => $v)

    {

        $line = explode(':',$v);

        if($line[0] == 'Content-Type') return str_replace('image/','',trim($line[1]));

    }

    return '';

}