How does php CURL get 500 errors returned by the opposite party?

I am using curl to ask
when the error is 500, for example,
how can I catch the information he spits out here with me?
because if there are no errors, the counterpart can send me a reply to json and receive it, it can show
, but it will send back 500 errors when the counterpart goes wrong, so how can I catch this piece of text?
I"ve been doing this for a long time, but I still haven"t caught

$ch = curl_init($api);
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
  curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: application/json"));
  curl_setopt($ch, CURLOPT_TIMEOUT, 5);
  curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
  $result = curl_exec($ch);

Php7 curl php json_encode json

Mar.03,2021

the

that can be obtained in the header information

// 
$headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);

// 
$header = substr($result, 0, $headerSize);

$httpCode = curl_getinfo ($ch, CURLINFO_HTTP_CODE);

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