PHP Error Handling

<?php
// Error levels:
// E_ERROR   — fatal, stops execution
// E_WARNING — non-fatal, script continues
// E_NOTICE  — minor issues (undefined variable)
// E_DEPRECATED — deprecated feature used
// E_ALL     — all errors

// Development: show all errors
error_reporting(E_ALL);
ini_set('display_errors', 1);

// Production: log errors, don't display
error_reporting(E_ALL);
ini_set('display_errors', 0);
ini_set('log_errors', 1);
ini_set('error_log', '/var/log/php_errors.log');

// Custom error handler
function myErrorHandler(int $errno, string $errstr,
                        string $errfile, int $errline): bool {
    echo "<b>Error [$errno]</b>: $errstr in $errfile on line $errline";
    return true; // don't execute PHP's internal error handler
}
set_error_handler("myErrorHandler");

// Trigger a notice
echo $undefinedVar; // triggers E_NOTICE
?>

<?php
function divide(int $a, int $b): float {
    if ($b === 0) {
        throw new InvalidArgumentException("Division by zero");
    }
    return $a / $b;
}

try {
    echo divide(10, 2);  // 5
    echo divide(10, 0);  // throws exception
} catch (InvalidArgumentException $e) {
    echo "Caught: " . $e->getMessage();
    echo " in " . $e->getFile() . " line " . $e->getLine();
} catch (Exception $e) {
    echo "General error: " . $e->getMessage();
} finally {
    echo "This always runs (cleanup code here)";
}
?>

<?php
// Custom exception classes
class DatabaseException extends RuntimeException {}
class ValidationException extends RuntimeException {
    private array $errors;

    public function __construct(array $errors, string $message = "") {
        parent::__construct($message ?: implode(", ", $errors));
        $this->errors = $errors;
    }

    public function getErrors(): array {
        return $this->errors;
    }
}

function validateAge(int $age): void {
    if ($age < 0 || $age > 150) {
        throw new ValidationException(
            ["Age must be between 0 and 150"],
            "Validation failed"
        );
    }
}

try {
    validateAge(200);
} catch (ValidationException $e) {
    echo $e->getMessage() . "\n";
    print_r($e->getErrors());
} catch (DatabaseException $e) {
    echo "DB Error: " . $e->getMessage();
}
?>