Slim redirect works; but also throws an exception - slim

Question

The following code correctly redirects; but also throws an exception:
$app->post("/foo", function () use ($app) {
try {
$app->redirect('/bar');
} catch (Exception $e) {
$app->log->debug("\n" . $e->getFile() . " (Line " . $e->getLine() . ") " . " - " . strftime('%c') . ": Exception (" . $e->getMessage() . ")");
$app->log->debug("\n" . $e->getTraceAsString());
}
});
This is from the Slim log:
/{site root}/Slim/Slim.php (Line 1017) - Wed Sep 17 17:51:33 2014: Exception ()
#0 /{site root}/Slim/Slim.php(1037): Slim\Slim->stop()
#1 /{site root}/Slim/Slim.php(1100): Slim\Slim->halt(302)
#2 /{site root}/index.php(328): Slim\Slim->redirect('/bar')
#3 [internal function]: {closure}()
#4 /{site root}/Slim/Route.php(462): call_user_func_array(Object(Closure), Array)
#5 /{site root}/Slim/Slim.php(1326): Slim\Route->dispatch()
#6 /{site root}/Slim/Middleware/Flash.php(85): Slim\Slim->call()
#7 /{site root}/Slim/Middleware/MethodOverride.php(92): Slim\Middleware\Flash->call()
#8 /{site root}/Slim/Middleware/PrettyExceptions.php(67): Slim\Middleware\MethodOverride->call()
#9 /{site root}/Slim/Slim.php(1271): Slim\Middleware\PrettyExceptions->call()
#10 /{site root}/index.php(689): Slim\Slim->run()
#11 {main}
What am I doing wrong? Or is this a bug in Slim? I can't find any mention of this particular issue.

Answer 1

Slim uses exceptions for route helpers, redirect being one of them. See the "Route Helpers" section in the documentation:
Please be aware that the following application instance method helpers
halt(), pass(), redirect() and stop() are implemented using
Exceptions. Each will throw a \Slim\Exception\Stop or
\Slim\Exception\Pass exception ...
This behavior can be surprising if unexpected.
There are code samples showing the behavior you're experiencing and how to avoid it. The trick is to redirect for error in the catch block and redirect for success after the try/catch block.