O Guia Definitivo do Yii 1.1

Note, code blocks need to be nested properly. That is, a code block cannot intersect with
another. It must be either at a parallel level or be completely enclosed by the other code
block.
To show profiling result, we need to install a CLogRouter application component with a
CProfileLogRoute log route. This is the same as we do with normal message routing. The
CProfileLogRoute route will display the performance results at the end of the current page.
Profiling SQL Executions
Profiling is especially useful when working with database since SQL executions are often
the main performance bottleneck of an application. While we can manually insert
beginProfile and endProfile statements at appropriate places to measure the time spent in
each SQL execution, starting from version 1.0.6, Yii provides a more systematic approach
to solve this problem.
By setting CDbConnection::enableProfiling to be true in the application configuration,
every SQL statement being executed will be profiled. The results can be readily displayed
using the aforementionedCProfileLogRoute, which can show us how much time is spent in
executing what SQL statement. We can also call CDbConnection::getStats() to retrieve the
total number SQL statements executed and their total execution time.
Erros
Yii provides a complete error handling framework based on the PHP 5 exception
mechanism. When the application is created to handle an incoming user request, it
registers its handleError method to handle PHP warnings and notices; and it registers its
handleException method to handle uncaught PHP exceptions. Consequently, if a PHP
warning/notice or an uncaught exception occurs during the application execution, one of
the error handlers will take over the control and start the necessary error handling
procedure.
Tip: The registration of error handlers is done in the application's constructor by calling
PHP functions set_exception_handler and set_error_handler. If you do not want Yii to
handle the errors and exceptions, you may define constant
YII_ENABLE_ERROR_HANDLER and YII_ENABLE_EXCEPTION_HANDLER to be
false in the entry script.
By default, errorHandler (or exceptionHandler) will raise an onError event (or onException
event). If the error (or exception) is not handled by any event handler, it will call for help
from the errorHandler application component.
Raising Exceptions
Raising exceptions in Yii is not different from raising a normal PHP exception. One uses
the following syntax to raise an exception when needed:
throw new ExceptionClass('ExceptionMessage');