首先,要有一台自己能控制的服务器和域名,因本人用的PHP,以下都以PHP语言为例。

在正式开发之前,先申请测试号用来测试

进入微信文档首页:http://mp.weixin.qq.com/wiki/home/index.html

测试号申请|在线调试->接口测试号申请

会要求你输入你的URL和Token

URL是用来验证服务器地址的有效性
Token自己设定,必须与你的URL中设的Token值相同

开发者提交信息后,微信服务器将发送GET请求到填写的服务器地址URL上,GET请求携带四个参数
signature
timestamp
nonce
echostr

开发者通过检验signature对请求进行校验(下面有校验方式)。若确认此次GET请求来自微信服务器,请原样返回echostr参数内容,则接入生效,成为开发者成功,否则接入失败。

参照给出的示例代码:
在服务器上新建index.php文件,确保通过域名http://www.xxx.com/index.php可以访问到,
index.php文件内容如下:

<?php
/**
  * wechat php test
  */

//define your token
define("TOKEN", "srrx");
$wechatObj = new wechatCallbackapiTest();
if(!isset($_GET["echostr"])) {
    if($wechatObj->checkSignature()) {
        $wechatObj->responseMsg();
    }
} else {
    $wechatObj->valid();
}


class wechatCallbackapiTest
{
    public function valid()
    {
        $echoStr = $_GET["echostr"];

        //valid signature , option
        if($this->checkSignature()){
            echo $echoStr;
            exit;
        }
    }

    public function responseMsg()
    {
        //get post data, May be due to the different environments
        $postStr = $GLOBALS["HTTP_RAW_POST_DATA"];

        //extract post data
        if (!empty($postStr)){
                /* libxml_disable_entity_loader is to prevent XML eXternal Entity Injection,
                   the best way is to check the validity of xml by yourself */
                libxml_disable_entity_loader(true);
                $postObj = simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
                $fromUsername = $postObj->FromUserName;
                $toUsername = $postObj->ToUserName;
                $keyword = trim($postObj->Content);
                $time = time();
                $textTpl = "<xml>
                            <ToUserName><![CDATA[%s]]></ToUserName>
                            <FromUserName><![CDATA[%s]]></FromUserName>
                            <CreateTime>%s</CreateTime>
                            <MsgType><![CDATA[%s]]></MsgType>
                            <Content><![CDATA[%s]]></Content>
                            <FuncFlag>0</FuncFlag>
                            </xml>";             
                if(!empty( $keyword ))
                {
                    $msgType = "text";
                    $contentStr = "Welcome to wechat world!!!";
                    $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
                    echo $resultStr;
                }else{
                    echo "Input something...";
                }

        }else {
            echo "";
            exit;
        }
    }
        
    public function checkSignature()
    {
        // you must define TOKEN by yourself
        if (!defined("TOKEN")) {
            throw new Exception('TOKEN is not defined!');
        }
        
        $signature = $_GET["signature"];
        $timestamp = $_GET["timestamp"];
        $nonce = $_GET["nonce"];
                
        $token = TOKEN;
        $tmpArr = array($token, $timestamp, $nonce);
        // use SORT_STRING rule
        sort($tmpArr, SORT_STRING);
        $tmpStr = implode( $tmpArr );
        $tmpStr = sha1( $tmpStr );
        
        if( $tmpStr == $signature ){
            return true;
        }else{
            return false;
        }
    }
}

?>

然后在提交URL和Token的地方填上"http://www.xxx.com/index.php"和在php文件里设的Token值"keyunq"

提交后,通过验证会给出成功提示。

然后用自己的微信号关注该测试号,输入任何内容,测试号会回复“Welcome to wechat world!!!”