微信分账,一直报这个错，不知道什么原因

    $dat='<xml>
    <appid>wx35ec6d7f8a84088d</appid>
    <mch_id>1541299971</mch_id>
    <nonce_str>'.random(32).'</nonce_str>
    <out_order_no>ME20191105131500813628</out_order_no>
    <transaction_id>4200000427201911052688896404</transaction_id>
    <sign>'.strtoupper(md5(trim($string1))).'</sign>
    <sign_type>HMAC-SHA256</sign_type>
    <receivers>
[
{
        "type"=>"PERSONAL_WECHATID",
      "account"=>"zmyzmy812",
      "amount"=>5,
      "description"=>"测试分到个人"
}
]
</receivers>
</xml>';
      $url="https://api.mch.weixin.qq.com/secapi/pay/profitsharing";
      $response = ihttp_request($url, $dat);
//    $response = $this->test($url,$dat);
      return $response;