It is always a good idea to use curl_close() on all individual curl handles after executing curl_multi_remove_handle(). This will free up additional memory resources. So, a typical code would look like:

<?php
$ch1 = curl_init();
curl_setopt($ch1, CURLOPT_URL, 'http://www.example.com/');
curl_setopt($ch1, CURLOPT_RETURNTRANSFER, true);

$ch2 = curl_init();
curl_setopt($ch2, CURLOPT_URL, 'http://www.example.net/');
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);

$mh = curl_multi_init();

curl_multi_add_handle($mh, $ch1);
curl_multi_add_handle($mh, $ch2);

$active = null;

do {
curl_multi_exec($mh, $active);
}
while($active);

$res1 = curl_multi_getcontent($ch1);
$res2 = curl_multi_getcontent($ch2);

curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);

curl_multi_close($mh);

curl_close($ch1);
curl_close($ch2);
?>