Using curl_multi_getcontent() to Retrieve Content from Multiple cURL Sessions in PHP

In PHP development, we often need to request data from other servers over the network. cURL (Client URL) is a powerful PHP extension library for network communication. cURL provides a series of functions, one of which is curl_multi_getcontent(), used to retrieve the content of a cURL session.

The curl_multi_getcontent() function obtains the content of a cURL session created by curl_multi_init(). When using curl_multi_exec() to execute multiple cURL sessions, we can call curl_multi_getcontent() to get each session's return result. The call is simple: just pass a cURL resource handle as the argument.

Below is an example code using curl_multi_getcontent():

// Initialize 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 sessions
do {
    $status = curl_multi_exec($mh, $active);
} while ($status === CURLM_CALL_MULTI_PERFORM || $active);

// Loop to retrieve each session's content
$contents = array();
foreach([$ch1, $ch2] as $ch) {
    $content = curl_multi_getcontent($ch);
    $contents[] = $content;
}

// Close the multi‑handle sessions
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 use curl_init() to initialize two cURL sessions and add them to a multi‑handle. Then we execute the sessions with curl_multi_exec(). During execution we call curl_multi_getcontent() to fetch each session's content and store it in an array. Finally we clean up with curl_multi_remove_handle() and curl_multi_close().

Note that before calling curl_multi_getcontent(), you must ensure the corresponding session has finished executing; otherwise the content may not be retrieved correctly.

In summary, curl_multi_getcontent() is a very useful function for obtaining the content of multiple cURL sessions. When making concurrent requests to several APIs, it allows you to fetch each session's response conveniently for further processing.