微信查询城市天气，首先，你需要找到一个获取天气的api，此处，用的是百度的apistore，可以去百度申请和使用api。
登录百度账号，并用手机发送请求获取apikey。有了apikey，可以按照它的示例来请求城市天气了。（可以按照城市中文名，拼音，城市编号等来查询）
你可以现在本地做测试，请求完成之后，再放到自己的域名空间的脚本里。
测试的脚本例如：（注意apikey填写自己申请的）
header('Content-type:text/html;charset=UTF-8');
$ch = curl_init();
$url = 'http://apis.baidu.com/apistore/weatherservice/cityname?cityname=上海';
$header = array(
'apikey: ',//你的apikey
);
// 添加apikey到header
curl_setopt($ch, CURLOPT_HTTPHEADER , $header);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
// 执行HTTP请求
curl_setopt($ch , CURLOPT_URL , $url);
$res = curl_exec($ch);
$res = json_decode($res, true);
echo "";
print_r($res);
echo "
";
$contentStr = "";
foreach($res as $k=>$v){
if($k == "retData"){
$contentStr = "城市：" . $v['city'] . "\n";
$contentStr .= "日期：" . $v['date'] . "\n";
$contentStr .= "天气：" . $v['weather'] ."\n";
$contentStr .= "平均气温：" . $v['temp'] . "℃\n";
$contentStr .= "最低气温：" . $v['l_tmp'] ."℃\n";
$contentStr .= "最高气温：" . $v['h_tmp'] . "℃\n";
$contentStr .= "风力：" . $v['WS'] . "\n";
$contentStr .= "风向：" . $v['WD'] . "\n";
$contentStr .= "日出时间：" . $v['sunrise'] . "\n";
$contentStr .= "日落时间：" . $v['sunset'] . "\n";
$contentStr .= "经度：" . $v['longitude'] . "\n";
$contentStr .= "纬度：" . $v['latitude'];
}
}
echo $contentStr;如果你填写了自己的apikey，那么应该能获取到所请求的天气了：
如果能返回正常的数据了，那么就可以放到你的域名空间里了。（公众平台里开发者中心填写的url，该url有连接微信接口等功能）
public function responseMsg(){
//get post data, May be due to the different environments
$postStr = $GLOBALS["HTTP_RAW_POST_DATA"]; //接收微信发来的XML数据
//extract post data
if(!empty($postStr)){
//解析post来的XML为一个对象$postObj
$postObj = simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
$fromUsername = $postObj->FromUserName; //请求消息的用户
$toUsername = $postObj->ToUserName; //"我"的公众号id
$keyword = trim($postObj->Content); //用户发送的消息内容
$time = time(); //时间戳
$msgtype = 'text'; //消息类型：文本
$textTpl = "
%s
";
if($postObj->MsgType == 'event'){ //如果XML信息里消息类型为event
if($postObj->Event == 'subscribe'){ //如果是订阅事件
$contentStr = "欢迎订阅misaka去年夏天！\n更多精彩内容：http://blog.csdn.net/misakaqunianxiatian";
$resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
echo $resultStr;
exit();
}
}
$which = mb_substr($keyword, 0, 2, 'UTF-8');//获取要返回什么样的信息
if($which== "翻译"){ //如果要进行翻译
//调用有道翻译API进行翻译
}elseif($which == "天气"){
$wea = $which;
$city = str_replace($wea, "", $keyword);
$ch = curl_init();
$url = 'http://apis.baidu.com/apistore/weatherservice/cityname?cityname=' . $city;
$header = array('apikey: '); //此处的apikey使用自己申请的apikey，填在冒号之后
// 添加apikey到header
curl_setopt($ch, CURLOPT_HTTPHEADER , $header);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
// 执行HTTP请求
curl_setopt($ch , CURLOPT_URL , $url);
$res = curl_exec($ch);
$res = json_decode($res, true);
$contentStr = "";
foreach($res as $k=>$v){
if($k == "retData"){
$contentStr = "城市：" . $v['city'] . "\n";
$contentStr .= "日期：" . $v['date'] . "\n";
$contentStr .= "天气：" . $v['weather'] ."\n";
$contentStr .= "平均气温：" . $v['temp'] . "℃\n";
$contentStr .= "最低气温：" . $v['l_tmp'] ."℃\n";
$contentStr .= "最高气温：" . $v['h_tmp'] . "℃\n";
$contentStr .= "风力：" . $v['WS'] . "\n";
$contentStr .= "风向：" . $v['WD'] . "\n";
$contentStr .= "日出时间：" . $v['sunrise'] . "\n";
$contentStr .= "日落时间：" . $v['sunset'] . "\n";
$contentStr .= "经度：" . $v['longitude'] . "\n";
$contentStr .= "纬度：" . $v['latitude'];
}
}
$resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
echo $resultStr;
exit();
}else{
$contentStr = "输入翻译XXX可以进行翻译(=・ω・=)\n\n输入天气XX可以查询城市天气";
$resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
echo $resultStr;
exit();
}完成之后（别忘了填写apikey），你的订阅号里，输入天气上海，那么应该能查到上海当天的天气了。
