问AuthFailure.SignatureFailure签名失败？

<?php
$secretID="0000000";
$secretKey="1111111111";
$param['Action']="DetectFace";
$param['Version']='2018-03-01';
$param['Nonce']=rand();
$param['Timestamp']=time();
$param["Region"]="ap-guangzhou";
$param["SecretId"]=$secretID;

$img = 'E:/softwaredownload/phpstudy/WWW/magicmirror/img/me.jpg';
$imgstr = base64_encode($img);
$param['Image']=$imgstr;

ksort($param);
$signStr="GETiai.tencentcloudapi.com/?";
foreach($param as $key => $value){
    $signStr = $signStr . $key . "=" . $value . "&";
}
$signStr = substr($signStr,0,-1);
$signature = urlencode(base64_encode(hash_hmac("sha1",$signStr,$secretKey,true)));
$param['Signature'] = $signature;

ksort($param);
$signStr="https://iai.tencentcloudapi.com/?";

foreach($param as $key => $value){
    $signStr = $signStr . $key . "=" . $value . "&";
}
$signStr = substr($signStr,0,-1);
echo $signStr;

$weather=curl_init();
curl_setopt($weather,CURLOPT_URL,$signStr);
curl_setopt($weather,CURLOPT_SSL_VERIFYPEER,false);
curl_setopt($weather,CURLOPT_RETURNTRANSFER,1);
curl_setopt($weather,CURLOPT_HTTPHEADER,array(
        'Content-Type:application/x-www-form-urlencoded',
        'Host: iai.tencentcloudapi.com'
        
    )
);
$data = curl_exec($weather);
echo $data;
?>