PHP卷曲错误的标题?

我正在将内容从PHP Curl脚本发送到API。

 $query = new stdClass; 
 $query->test = 'test';
 $query = json_encode($query);
 $ch = curl_init();         
 curl_setopt($ch, CURLOPT_URL, 'http://localhost');
 curl_setopt($ch, CURLOPT_HEADER, ['Content-Type: application/json', 'Content-Length: '.strlen($query)]);
 curl_setopt($ch, CURLOPT_POST, true);
 curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 60);
 curl_setopt($ch, CURLOPT_POSTFIELDS, $query);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false); 
 curl_setopt($ch, CURLOPT_VERBOSE, true);               
 $res = curl_exec($ch);
 curl_close($ch);  

但是当我在API端跟踪请求的内容类型时,我得到

 var_dump($_SERVER['CONTENT_TYPE']);
 //application/x-www-form-urlencoded

 application/json