meet it

Give your exceptions a family tree, then catch whole branches.

Big apps build an : one parent like ShopException, with children such as OutOfStock and CardDeclined. Catching the parent catches every child, so one block handles anything your shop throws, while PHP's own errors still get through.

To catch two unrelated types the same way, join them with a bar in one : catch (TooLong | Reserved $e). At the very top of PHP's tree sits , which every exception and error implements.

And finally runs last, whatever happened: success, a caught exception, even one that escapes. Use it to tidy up.

<?php
class ShopException extends Exception {}
class OutOfStock extends ShopException {}
class CardDeclined extends ShopException {}
foreach ([1200, 9900] as $pence) {
    try {
        if ($pence > 5000) {
            throw new CardDeclined("Card declined for $pence pence.");
        }
        echo "Paid $pence pence.\n";
    } catch (ShopException $e) {
        echo get_class($e) . ": " . $e->getMessage() . "\n";
    } finally {
        echo "Receipt printed.\n";
    }
}

Catching Throwable everywhere hides real bugs, so save it for the very outside of your app.

guess first

A `return` and a `finally`. What will this show?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

<?php
function load(string $file): string {
    try {
        if ($file === "") {
            throw new InvalidArgumentException("No file name");
        }
        return "Loaded $file";
    } finally {
        echo "Closing up\n";
    }
}
echo load("notes.txt") . "\n";

your turn

Your turn. Check a new username.

Type a username in the first blank: try a long one, admin, or a good one. Then catch both exception types in one block with a bar between them.

Your code

press run to see what happens

fix it

The admin page escapes the safety net. Fix it.

Broken code to fix

press run to see what happens

The first page is caught, then an uncaught Forbidden stops the run. Which family does Forbidden belong to?
catch (AppException $e) only catches AppException and its children. Look at what each class on lines 3 and 4 extends.
On line 4, make Forbidden extend AppException, then run it.

nailed it

you built a family tree of problems. :D

Catching a parent exception also catches all of its children.
Join types with | to catch them in one block.
finally always runs, so use it to tidy up.

new words in your collection

exception hierarchy
Throwable
multi-catch

This lesson isn’t saved. A free account remembers every lesson you finish.

Give your exceptions a family tree, then catch whole branches.

A return and a finally. What will this show?

Your turn. Check a new username.

The admin page escapes the safety net. Fix it.

you built a family tree of problems. :D

A `return` and a `finally`. What will this show?