PHP curl post length required error setting header header

The problem is parameters

  $param=array(
            'grant_type'=>'authorization_code',
            'code'=>$code,
            'redirect_uri'=>$redirect_uri
        );

Change to ：

$param="grant_type=authorization_code&code=".$code."&redirect_uri=".$redirect_uri;

 $header = [];
        array_push($header, "Authorization:Basic " . $base,"Content-type:x-www-form-urlencoded","Content-length:".strlen ($param));

 

$curl = curl_init();
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "GET");
curl_setopt($curl, CURLOPT_HTTPHEADER, array('Expect:'));
curl_setopt($curl, CURLOPT_URL, $postUrl);
curl_setopt($curl, CURLOPT_TIMEOUT, 15);
curl_setopt($curl, CURLOPT_HTTPHEADER, $header);
curl_setopt($curl, CURLOPT_FAILONERROR, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_HEADER, false);