From start to finish: How to use php extension cURL for HTTP requests

Introduction:
In web development, it is often necessary to communicate with third-party APIs or other remote servers. Using cURL to make HTTP requests is a common and powerful way. This article will introduce how to use PHP to extend cURL to perform HTTP requests, and provide some practical code examples.

1. Preparation
First, make sure that php has the cURL extension installed. You can execute php -m | grep curl on the command line to check whether it is installed. If it is not installed, you can install it by following the steps below:

1. On Linux systems, use the following command to install the cURL extension:
   sudo apt-get install php-curl
2. On Windows systems, edit the php.ini file, find the line extension=php_curl.dll, and remove the comment symbol (;).
3. Restart the web server, such as Apache or Nginx.

2. Perform GET request
GET request is the most common HTTP request type. Here is a sample code that uses cURL to perform a GET request:

$url = 'https://api.example.com/users';
$ch = curl_init($url);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
curl_close($ch);

if ($response === false) {
    echo '請求失敗';
} else {
    echo '響應內(nèi)容：' . $response;
}

The above code first initializes the cURL session, sets the requested URL, and sets some options through the curl_setopt function. Among them, the CURLOPT_RETURNTRANSFER option is used to set the response result to be returned instead of outputting it directly to the screen. Then, use the curl_exec function to send the request and get the response result. Finally, close the session through the curl_close function.

3. Execute POST request
POST request is mainly used to submit data to the server, such as form data, etc. The following is a sample code that uses cURL to perform a POST request:

$url = 'https://api.example.com/users';
$fields = array(
    'name' => 'John Doe',
    'email' => 'john@example.com'
);

$ch = curl_init($url);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($fields));

$response = curl_exec($ch);
curl_close($ch);

if ($response === false) {
    echo '請求失敗';
} else {
    echo '響應內(nèi)容：' . $response;
}

In addition to setting the CURLOPT_POST option to true, the above code also uses the CURLOPT_POSTFIELDS option to set the POST request. data. The http_build_query function is used here to convert the array into a string in URL parameter format.

4. Processing the response
In HTTP requests, it is often necessary to check the status code of the response to determine whether the request is successful, and to process the returned data. Here is a sample code that demonstrates how to handle the response:

$url = 'https://api.example.com/users';
$ch = curl_init($url);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

curl_close($ch);

if ($httpCode == 200) {
    // 請求成功
    $data = json_decode($response, true);
    // 處理返回的數(shù)據(jù)
} else {
    // 請求失敗
    echo '請求失敗，狀態(tài)碼：' . $httpCode;
}

The code above uses the curl_getinfo function to get the transfer information, including the HTTP status code. Determine whether the request is successful based on the status code, and process the returned data according to requirements.

5. Set other options
cURL provides many other options to meet more complex needs. The following are some commonly used options:

1. CURLOPT_HEADER: Set whether to return response headers, the default is false.
2. CURLOPT_TIMEOUT: Set the request timeout in seconds. The default is 0, which means there is no timeout limit.
3. CURLOPT_USERAGENT: Set the User-Agent header to simulate the browser identity.
4. CURLOPT_SSL_VERIFYPEER: Set whether to verify the server SSL certificate. The default is true.

6. Summary
This article introduces how to use php to extend cURL to make HTTP requests, and provides some practical code examples. By mastering the use of cURL, you can easily communicate with the remote server and obtain the required data. At the same time, pay attention to security and error handling to ensure the reliability of requests.

Finally, I hope readers can learn the basic knowledge about cURL through this article and use it flexibly in actual development. Thanks for reading!

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