PHP连接IP库查找物理地址(城市)代码

PHP根据IP查找物理地址，这个是个例子，需要连接网上的IP库来查询，准确与否取决于网上IP地址库是否精确，本函数介绍其实现过程：

<?php
function detect_city($ip){
  $default = 'UNKNOWN';
  if (!is_string($ip) || strlen($ip) < 1 || $ip == '127.0.0.1' || $ip == 'localhost')
      $ip = '8.8.8.8';
  $curlopt_useragent = 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)';
  $url = 'http://ipinfodb.com/ip_locator.php?ip='.urlencode($ip);
  $ch = curl_init();
  $curl_opt = array(
      CURLOPT_FOLLOWLOCATION => 1,
      CURLOPT_HEADER => 0,
      CURLOPT_RETURNTRANSFER => 1,
      CURLOPT_USERAGENT => $curlopt_useragent,
      CURLOPT_URL => $url,
      CURLOPT_TIMEOUT => 1,
      CURLOPT_REFERER => 'http://'. $_SERVER['HTTP_HOST'],
  );
  curl_setopt_array($ch, $curl_opt);
  $content = curl_exec($ch);
  if (!is_null($curl_info)){
      $curl_info = curl_getinfo($ch);
  }
  curl_close($ch);
  if ( preg_match('{<li>City : ([^<]*)</li>}i', $content, $regs) ){
      $city = $regs[1];
  }
  if ( preg_match('{<li>State/Province : ([^<]*)</li>}i', $content, $regs) ){
      $state = $regs[1];
  }
  if( $city!='' && $state!='' ){
    $location = $city . ', ' . $state;
    return $location;
  }else{
    return $default;
  }
}
?>

用法示例：

echo detect_city('216.19.128.171');

来源：http://www.codefans.net/articles/1231.shtml