PHP — Form Handling

Basic try-catch

<?php
try {
    $result = 10 / 0;
} catch (DivisionByZeroError $e) {
    echo "Error: " . $e->getMessage();
}
?>

Custom exceptions

<?php
class InsufficientFundsException extends Exception {
    public function __construct(float $amount) {
        parent::__construct("Insufficient funds: need $amount");
    }
}

class BankAccount {
    private float $balance;

    public function __construct(float $initial) {
        $this->balance = $initial;
    }

    public function withdraw(float $amount): void {
        if ($amount > $this->balance) {
            throw new InsufficientFundsException($amount - $this->balance);
        }
        $this->balance -= $amount;
    }
}

try {
    $acc = new BankAccount(100);
    $acc->withdraw(150);
} catch (InsufficientFundsException $e) {
    echo $e->getMessage();
}
?>

Multiple catch blocks

<?php
try {
    $data = json_decode("invalid", true);
    if (json_last_error() !== JSON_ERROR_NONE) {
        throw new Exception("JSON error");
    }
} catch (TypeError $e) {
    echo "Type error: " . $e->getMessage();
} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
} finally {
    echo "Cleanup";
}
?>

Finally block

<?php
function readConfig(string $path): array {
    $file = null;
    try {
        $file = fopen($path, 'r');
        return json_decode(fread($file, filesize($path)), true);
    } catch (Exception $e) {
        return [];
    } finally {
        if ($file) fclose($file);
    }
}
?>

Exception chaining

<?php
try {
    try {
        throw new Exception("Original error");
    } catch (Exception $e) {
        throw new Exception("Wrapper error", 0, $e);
    }
} catch (Exception $e) {
    echo $e->getMessage();
    echo $e->getPrevious()->getMessage();
}
?>

Mini Practice

Write PHP code that:

1. Creates a custom exception
2. Uses try-catch-finally
3. Chains exceptions
4. Handles multiple exception types

Up Next

In the next lesson, you'll learn about File Handling — reading and writing files.