我写了一个简单地类来实现推送文本的功能，企业号个人可以免费注册。
微信企业号接口文档：http://qydev.weixin.qq.com/wiki/

$weixinsend = new weixin("CorpID","Secret");//实例化
var_dump($weixinsend->send_text("admin","","","0","测试"));
//$weixin->send_text("你的id","接收部门id","接收标签id","应用id","文本")
//返回false说明发送成功，发送失败返回错误消息
class weixin {
 private $appId;
 private $appSecret;
 public function __construct($appId, $appSecret) {
  $this->appId = $appId;
  $this->appSecret = $appSecret;
 }
  public function send_text($touser,$toparty,$totag,$agentid,$text,$safe="0") {
    /*
    消息类型msgtype text文本发送
    $touser 接收user 可选 |号隔开多个
    $toparty 接收部门 可选 |号隔开多个
    $totag 接收标签 可选 |号隔开多个
    $agentid 应用id 整型
    $text 发送内容 json
    $safe 是否加密 可选 布尔值
    */
    $post_text=array(
      'touser' => $touser, 
      'toparty' => $toparty, 
      'totag' => $totag, 
      'msgtype' => "text", //默认消息类型文本
      'agentid' => $agentid, 
      'text' => array('content'=>$text), 
      'safe' => $safe,       
      );
    $accessToken = $this->getAccessToken();
    $output= json_encode($post_text,JSON_UNESCAPED_UNICODE);
    $output= $this->http_post_get("https://qyapi.weixin.qq.com/cgi-bin/message/send?access_token=$accessToken","$output");
    return $this->err_echo($output);
  }
  private function getAccessToken() {
    //文本形式存储token，建议改造成适合自己的
    $data = json_decode(file_get_contents("access_token.json"));//获取口令
    if ($data->expire_time < time()) {//重新获取
      $url = "https://qyapi.weixin.qq.com/cgi-bin/gettoken?corpid=$this->appId&corpsecret=$this->appSecret";
      $res = json_decode($this->http_get($url));
      $access_token = $res->access_token;
      if ($access_token) {
        $data->expire_time = time() + 7000;//应该是7200秒有效期 这样写容错
        $data->access_token = $access_token;
        $fp = fopen("access_token.json", "w");
        fwrite($fp, json_encode($data));
        fclose($fp);
      }
    } else {
      $access_token = $data->access_token;
    }
    return $access_token;
  }
  public function err_echo($errcode){
    $err=json_decode($errcode,TRUE);
    if ($err['errcode']){
      return $err['errmsg'];//错误消息
      //return $err['errcode'];//错误代码
    }
    return false;
  }
  public function http_post_get($url, $rawData)  {
    //post返回
    $headers = array("Content-Type: text/xml; charset=utf-8");
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $rawData);
    curl_setopt($ch, CURLOPT_TIMEOUT, 20);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    curl_setopt($ch, CURLOPT_URL, $url);
    $output = curl_exec($ch);
    curl_close($ch);
    return $output;
  }
  private function http_get($url) {
    //获取token
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 20);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
    curl_setopt($curl, CURLOPT_URL, $url);
    $res = curl_exec($curl);
    curl_close($curl);
    return $res;
  }
}