下载远程图片

/**
 * 下载远程文件
 * @param  string  $url     网址
 * @param  string  $filename    保存文件名
 * @param  integer $timeout 过期时间
 * return boolean|string
 */
function http_down($url, $dir, $timeout = 60) {
    preg_match('/mmbiz_[\w]+/i', $url,$a);
    $ext = explode('_', $a[0])[1];
    $filename = $dir.md5(time().mt_rand()).'.'.$ext;

	ini_set('php_curl','on');
    $path = dirname($filename);
    if (!is_dir($path) && !mkdir($path, 0755, true)) {
        return false;
    }
    $fp = fopen($filename, 'w');
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_FILE, $fp);
    curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    curl_exec($ch);
    curl_close($ch);
    fclose($fp);
    return $filename;
}