Using PHP curl_multi_add_handle() to Manage Multiple cURL Handles

The PHP curl library is a widely used tool for performing HTTP requests such as GET and POST, setting headers, and handling cookies.

When many requests need to be sent simultaneously, creating a separate cURL handle for each can waste resources; the curl_multi_add_handle() function allows multiple handles to be added to one multi‑handle session for efficient management.

The syntax of curl_multi_add_handle() is:

resource curl_multi_add_handle ( resource $mh , resource $ch )

$mh is an initialized cURL multi‑handle, and $ch is the individual cURL handle to be added; the function returns a cURL multi‑handle.

Below is a practical example that initializes a multi‑handle, creates two independent cURL handles for different URLs, adds them to the multi‑handle, executes the requests in a loop until all are complete, retrieves each response, and finally removes the handles and closes the session.

<?php
$mh = curl_multi_init();  // initialize multi‑handle

$ch1 = curl_init();
curl_setopt($ch1, CURLOPT_URL, "https://www.example.com/api1");
curl_setopt($ch1, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch1);  // add first handle

$ch2 = curl_init();
curl_setopt($ch2, CURLOPT_URL, "https://www.example.com/api2");
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);
curl_multi_add_handle($mh, $ch2);  // add second handle

// execute until all requests are done
do {
    $status = curl_multi_exec($mh, $running);
} while ($status === CURLM_CALL_MULTI_PERFORM || $running);

// get results
$response1 = curl_multi_getcontent($ch1);
echo "Response 1: " . $response1 . "\n";
$response2 = curl_multi_getcontent($ch2);
echo "Response 2: " . $response2 . "\n";

// clean up
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);
curl_multi_close($mh);
?>

The example demonstrates initializing the multi‑handle with curl_multi_init() , creating two separate handles ( $ch1 and $ch2 ), adding them to the session, looping with curl_multi_exec() until completion, retrieving each response via curl_multi_getcontent() , and finally cleaning up with curl_multi_remove_handle() and curl_multi_close() .

Using curl_multi_add_handle() together with related functions such as curl_multi_remove_handle() and curl_multi_close() enables efficient management of multiple concurrent network requests, improving performance and code maintainability in PHP backend development.