Graceful error trapping and display is important, both during development and after deployment. It is also good to have debug control that is manageable through environment variables. One nice solution is to use SetEnv in .htaccess or a .conf file.

Regardless of the trap and display code, be sure to log all errors, so you can resolve them if they occur. Check the error log (usually /etc/httpd/logs/error_log) frequently.

Along those lines, although using isset in Smarty template will not cause an error, if the Smarty variable inside the call is not set, a PHP will be thrown (http://smarty.net/manual/en/language.modifier.default.php). Possible solutions:

• Do nothing - disk space is cheap and the logs get rotated (this is the wrong answer)
• Initialize all Smarty variables for the templates in the PHP (a good answer)
• Use PHP to initialize the template variables within the template, using {php} tags (also a valid approach)
• Use AJAX to populate forms (may be much more difficult and take longer)

The best approach depends on the application architecture, and may vary by template within the application.

It is good to look at the compiled templates to see how they are constructed.