Errors and Exceptions

<?php

declare(strict_types=1);

function loanDays(string $format): int
{
    return match ($format) {
        'hardcover', 'paperback' => 21,
        'ebook' => 14,
    };
}

foreach (['ebook', 'vinyl'] as $format) {
    try {
        $days = loanDays($format);              // may throw before anything is printed
        echo "{$format}: {$days} days\n";
    } catch (UnhandledMatchError $e) {
        echo "{$format}: not lendable ({$e->getMessage()})\n";
    } finally {
        echo "-- checked {$format}\n";
    }
}

try {
    json_decode('{"title": ', flags: JSON_THROW_ON_ERROR);
} catch (JsonException | ValueError) {           // multi-catch, no variable (8.0)
    echo "invalid JSON\n";
}

ebook: 14 days
-- checked ebook
vinyl: not lendable (Unhandled match case 'vinyl')
-- checked vinyl
invalid JSON

<?php

declare(strict_types=1);

final class BookNotAvailable extends RuntimeException
{
    public static function becauseOnLoan(string $isbn, ?Throwable $previous = null): self
    {
        return new self("Book {$isbn} is on loan", 409, $previous);
    }
}

function lend(string $isbn, array $onLoan): string
{
    try {
        if (in_array($isbn, $onLoan, true)) {
            throw new DomainException('loan record exists');
        }
        return "lent {$isbn}";
    } catch (DomainException $e) {
        throw BookNotAvailable::becauseOnLoan($isbn, $e);     // chain the cause
    }
}

try {
    lend('978-0-00-000001-1', ['978-0-00-000001-1']);
} catch (BookNotAvailable $e) {
    printf("%s (code %d), caused by: %s\n", $e->getMessage(), $e->getCode(), $e->getPrevious()?->getMessage());
}
// Book 978-0-00-000001-1 is on loan (code 409), caused by: loan record exists

; development
error_reporting = E_ALL
display_errors = On
log_errors = On

; production
error_reporting = E_ALL & ~E_DEPRECATED
display_errors = Off
display_startup_errors = Off
log_errors = On
error_log = /var/log/php/error.log
zend.exception_ignore_args = On

<?php

declare(strict_types=1);

set_error_handler(static function (int $level, string $message, string $file, int $line): bool {
    if (!(error_reporting() & $level)) {
        return false;                       // respect error_reporting and the @ operator
    }
    throw new ErrorException($message, 0, $level, $file, $line);
});

set_exception_handler(static function (Throwable $e): void {
    error_log(sprintf('[%s] %s in %s:%d', $e::class, $e->getMessage(), $e->getFile(), $e->getLine()));
    fwrite(STDERR, "Something went wrong; the incident was logged.\n");
});

var_dump(get_error_handler() instanceof Closure);   // bool(true) -- 8.5

try {
    $titles = ['Kindred'];
    echo $titles[3];                                 // warning -> ErrorException
} catch (ErrorException $e) {
    echo get_class($e), ': ', $e->getMessage(), ' (', $e->getSeverity() === E_WARNING ? 'E_WARNING' : 'other', ")\n";
}
// ErrorException: Undefined array key 3 (E_WARNING)

<?php

declare(strict_types=1);

function registerFormat(): void
{
    new class implements Countable {};    // compile error raised while running: missing count()
}

function boot(): void
{
    registerFormat();
}

boot();

Fatal error: Class Countable@anonymous must implement 1 abstract method (Countable::count) in ... on line 7
Stack trace:
#0 ...(12): registerFormat()
#1 ...(15): boot()
#2 {main}