Mastering curl_multi_getcontent(): Retrieve Multiple cURL Sessions in PHP

In PHP development we often need to request data from other servers, and cURL (Client URL) is a powerful extension for network communication. One of its functions, curl_multi_getcontent(), is used to retrieve the content of a cURL session.

The curl_multi_getcontent() function obtains the content of a handle created by curl_multi_init() after the multi handle has been executed with curl_multi_exec(). It simply requires a cURL resource handle as its argument.

Below is a complete example demonstrating how to use curl_multi_getcontent():

// Initialize two cURL sessions
$ch1 = curl_init('http://www.example.com/api1');
$ch2 = curl_init('http://www.example.com/api2');

// Create a new multi handle
$mh = curl_multi_init();

// Add the two sessions to the multi handle
curl_multi_add_handle($mh, $ch1);
curl_multi_add_handle($mh, $ch2);

// Execute the multi handle
do {
    $status = curl_multi_exec($mh, $active);
} while ($status === CURLM_CALL_MULTI_PERFORM || $active);

// Retrieve the content of each session
$contents = [];
foreach ([$ch1, $ch2] as $ch) {
    $content = curl_multi_getcontent($ch);
    $contents[] = $content;
}

// Remove handles and close the multi handle
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);

// Output the retrieved contents
var_dump($contents);

In the code above we first initialize two cURL sessions with curl_init(), add them to a multi handle, execute them with curl_multi_exec(), and then use curl_multi_getcontent() inside a loop to fetch each session's response, storing the results in an array. Finally we remove the handles and close the multi handle.

It is important to ensure that a session has completed execution before calling curl_multi_getcontent(); otherwise the function may not return the expected data.

In summary, curl_multi_getcontent() is a very useful function for obtaining the content of multiple concurrent cURL sessions, making it easier to handle the results of parallel API requests.