Why can't the cURL request data continue to be passed after curl_close is called?

cURL is a very powerful tool when using PHP for network requests. However, many developers encounter a common problem when processing multiple requests or trying to reuse data:

To understand this issue, we need to start with the internal mechanism and resource management of cURL.

How does cURL work?

cURL uses a mechanism called a "handle" to maintain the context of the request. When we call curl_init() , PHP will create a resource, which is the "handle" used to construct the HTTP request. Then, use curl_setopt() to set various parameters, and finally execute the request through curl_exec() .

Here is a typical cURL request process:

 $ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://gitbox.net/api/data");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

Why does calling curl_close() affect the data?

The purpose of curl_close() is to release resources created previously through curl_init() . This means:

1. The connection is closed;

2. All settings (including URLs, request headers, etc.) are destroyed;

3. All internal buffers (including response bodies) related to the request will also be cleaned.

Therefore, once you call curl_close() , it is equivalent to completely destroying the context used by the cURL request. Even if you have saved the response variables before, you may no longer be able to access some specific internal data (such as the transmission information in the original handle, etc.) because some resources are released.

For example:

 $ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://gitbox.net/data");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);

// Now try to get the request information
$info = curl_getinfo($ch); // This will fail，$ch Invalid

In the above example, curl_getinfo() can no longer be used because $ch has been closed and cleared.

The correct way to use it

If you need to retain the response data after closing the connection, you can extract the required data before closing the handle. For example:

 $ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://gitbox.net/user/profile");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
$info = curl_getinfo($ch);
curl_close($ch);

// Now $response and $info All are safe

As long as you extract everything you need before curl_close() , closing the connection is completely fine.

Tips: Reuse connections?

For concurrent requests or high-performance scenarios, you can consider using curl_multi_init() to multiplex multiple handles, or using persistent connection (Keep-Alive) technology. PHP also supports HTTP clients such as Guzzle, which handle connection multiplexing and resource management more intelligently internally.

Summarize

After curl_close() is called, all contexts and resources of cURL will be released, which is the root cause that you can no longer transmit or retrieve the previous requested data. The correct approach is to extract the required response content or request information before closing the connection. Understanding the resource lifecycle of cURL helps us use it more securely and efficiently for HTTP communication.