You should close a PHP/CURL session immediately after you are done using it, as shown in Listing A-23. Closing the PHP/CURL session frees up server resources, primarily memory.

curl_close($s);

Listing A-23: Closing a PHP/CURL session

In normal use, PHP performs garbage collection, freeing resources like variables, socket connections, and memory when the script completes. This works fine for scripts that control web pages and execute quickly. However, webbots and spiders may require that PHP scripts run for extended periods without garbage collection. (I've written webbot scripts that run for months without stopping.) Closing each PHP/CURL session is imperative if you're writing webbot and spider scripts that make many PHP/CURL connections and run for extended periods of time.