当CURLOPT_HTTPHEADER需要'Content-Length'时

Question

I have this code in the client side of my application:

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET"); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
curl_setopt($ch, CURLOPT_HTTPHEADER, array( 
    'Content-Type: application/json', 
    'Content-Length:0 ' ) 
    ); 
$body = curl_exec($ch);

while in the server files:

$ch = curl_init($this->modelAddress);
$data = array("params"=>array("resource" => "artist","operation" => $operation,"params"=>$params));
$data_string = json_encode($data);

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");                                                                     
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);                                                                  
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);                                                                      
curl_setopt($ch, CURLOPT_HTTPHEADER, array(                                                                          
    'Content-Type: application/json',                                                                                
    'Content-Length: ' . strlen($data_string))                                                                       
);

They are made from 2 different people and I want to ask what is the most correct.
When the use of 'Content-Length:0' instead of 'Content-Length:'.strlen($data_string) is better.

It's only question of POST/GET method?
I've searched explanations of this in the web but I've found nothing

Answer 1

If you use http PUT with curl then you have to specify the Content-Length header. Otherwise it is automatically handled by the curl for both GET and POST.

For example if you are posting the following data with curl with CURLOPT_POSTFIELDS. Then curl will automatically add the length of the data with the header.

$data = "name=alex&email=none!";
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);

For better understand, run your curl code using verbose mode and you'll see how its handling the requests and responses.

curl_setopt($ch, CURLOPT_VERBOSE, true);