What are common pitfalls when using the Smarty template engine in PHP, as seen in the forum thread?

Common pitfalls when using the Smarty template engine in PHP include not properly escaping user input to prevent XSS attacks, using too many nested template files which can lead to performance issues, and not utilizing caching effectively which can slow down the application. To prevent XSS attacks, always escape user input using Smarty's escape modifier. To improve performance, limit the number of nested template files and consider using caching to store compiled templates.

// Example of escaping user input in Smarty template
{$userInput|escape}

// Example of limiting nested template files
{include file="header.tpl"}
{include file="content.tpl"}
{include file="footer.tpl"}

// Example of utilizing caching in Smarty
$smarty->caching = true;
$smarty->cache_lifetime = 3600; // 1 hour