meet it

and turn a crash into a plan B.

An exception does not have to end your program. Put the risky code in a try block. If anything inside throws, PHP jumps straight to the catch block, then carries on after it.

catch (InvalidArgumentException $e) names the kind it catches and puts the exception in $e. hands back its message, ready to show the visitor. Catch the kind you expect, such as PDOException for database trouble, so surprises still show up.

A block after them always runs, thrown or not. It suits tidying up, like a closing message.

<?php
function check_age(int $age): int {
    if ($age < 0) { throw new InvalidArgumentException("Age cannot be negative"); }
    return $age;
}
try {
    echo "Age: " . check_age(-3) . "\n";
} catch (InvalidArgumentException $e) {
    echo "Sorry: " . $e->getMessage() . "\n";
} finally {
    echo "Thanks for visiting\n";
}

Nothing in the try after the throw runs, not even the rest of that line.

guess first

There is no orders table. What will this show?

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

<?php
$db = new PDO("sqlite::memory:");
try {
    $db->exec("INSERT INTO orders VALUES (1)");
    echo "Order saved\n";
} catch (PDOException $e) {
    echo "Could not save the order\n";
}
echo "Carry on shopping\n";

your turn

Your turn. Handle a silly quantity.

Type a quantity, like 3, then run it. Then try something silly, like lots or -2, and see the friendly message.

Your code

press run to see what happens

fix it

The catch never catches. Can you fix it?

Broken code to fix

press run to see what happens

The program still stops with an error. What kind of exception does it name?
The database throws a PDOException, but the catch only catches InvalidArgumentException.
Change line 6 to } catch (PDOException $e) {, then press run.

nailed it

your program keeps calm when things go wrong. :D

Risky code goes in try, and plan B in catch.
$e->getMessage() gives the exception's message.
finally always runs, thrown or not.

new words in your collection

try
catch
finally
getMessage

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

try and catch turn a crash into a plan B.

There is no orders table. What will this show?

Your turn. Handle a silly quantity.

The catch never catches. Can you fix it?

your program keeps calm when things go wrong. :D

and turn a crash into a plan B.