diff --git a/inc/error.php b/inc/error.php
index 4c8eb19e..fed211ac 100644
--- a/inc/error.php
+++ b/inc/error.php
@@ -1,9 +1,222 @@
 <?php
+namespace Vichan;
 
-function error_handler($errno, $errstr, $errfile, $errline) {
-	if (error_reporting() & $errno) {
-		$config['debug'] = true;
-		error("$errstr in $errfile at line $errline");
+class ErrorHandler {
+	private static array|false $error_recursion = false;
+
+	private bool $include_details;
+	/**
+	 * @var callable
+	 */
+	private mixed $logger_fn;
+
+
+	private static function isCli(): bool {
+		return defined('STDIN') || \PHP_SAPI === 'cli' || (\stristr(\PHP_SAPI, 'cgi') && \getenv('TERM'))
+			|| (empty($_SERVER['REMOTE_ADDR']) && !isset($_SERVER['HTTP_USER_AGENT']) && \count($_SERVER['argv']) > 0);
+	}
+
+	private static function errnoToLogLevel(int $errno): int {
+		switch ($errno) {
+			default:
+			case \E_ERROR:
+			case \E_PARSE:
+			case \E_CORE_ERROR:
+			case \E_COMPILE_ERROR:
+			case \E_RECOVERABLE_ERROR:
+				return \LOG_EMERG;
+			case \E_USER_ERROR:
+				return \LOG_ERR;
+			case \E_WARNING:
+			case \E_CORE_WARNING:
+			case \E_COMPILE_WARNING:
+			case \E_USER_WARNING:
+				return \LOG_WARNING;
+			case \E_NOTICE:
+			case \E_DEPRECATED:
+			case \E_USER_NOTICE:
+			case \E_USER_DEPRECATED:
+				return \LOG_NOTICE;
+		}
+	}
+
+	public static function handle_error(
+		int $level,
+		string $message,
+		callable $logger,
+		bool $display_details,
+		string $file,
+		int $line,
+		string $trace_str,
+		array $trace
+	): void {
+		global $board, $mod, $config, $db_error;
+
+		$newline = self::isCli() ? '\n' : '<br>';
+
+		if (self::$error_recursion !== false) {
+			list($o_message, $o_file, $o_line, $o_trace) = self::$error_recursion;
+			if ($display_details) {
+				echo("Error recursion detected with $message at $file:$line. Backtrace:$newline$trace_str{$newline}Original error: $o_message at $o_file:$o_line. Original backtrace:$newline$o_trace");
+			} else {
+				echo("Error recursion detected with $message{$newline}Original error: $o_message");
+			}
+			exit;
+		}
+
+		self::$error_recursion = [ $message, $file, $line, $trace_str ];
+
+		// Message for the system, be it cli or error logging facility.
+		$sys_msg = "Error: $message at $file:$line.\nBacktrace: $trace_str\n";
+
+		if (self::isCli()) {
+			// Running from CLI. Always display the details.
+			echo($sys_msg);
+			exit;
+		}
+
+		// Log the error if we aren't running from cli.
+		$logger($level, $sys_msg);
+
+		// Recycled code.
+		$debug_stuff = [];
+		if ($config['debug']) {
+			if (isset($db_error)) {
+				$debug_stuff = \array_combine([ 'SQLSTATE', 'Error code', 'Error message' ], $db_error);
+			}
+			$debug_stuff['backtrace'] = $trace;
+
+			// Remove the password from SQL errors.
+			$pw = $config['db']['password'];
+			$debug_callback = function($item) use (&$debug_callback, $pw) {
+				if (\is_array($item)) {
+					$item = \array_filter($item, $debug_callback);
+				}
+				return $item !== $pw || !$pw;
+			};
+			$debug_stuff = \array_map($debug_callback, $debug_stuff);
+		}
+
+		\header("{$_SERVER['SERVER_PROTOCOL']} 500 Internal Server Error");
+
+		// Error via json.
+		if (isset($_POST['json_response'])) {
+			\header('Content-Type: text/json; charset=utf-8');
+			$data = [ 'error' => $message ];
+			if (!empty($config) && $config['debug'] && !empty($debug_stuff)) {
+				$data['debug'] = $debug_stuff;
+			}
+			echo(\json_encode($data));
+			exit;
+		}
+
+		// Pretty print.
+		die(Element('page.html', [
+			'config' => $config,
+			'title' => _('Error'),
+			'subtitle' => _('An error has occured.'),
+			'body' => Element('error.html', [
+				'config' => $config,
+				'message' => $message,
+				'mod' => $mod,
+				'board' => isset($board) ? $board : false,
+				'debug' => \str_replace("\n", '&#10;', utf8tohtml(print_r($debug_stuff, true)))
+			])
+		]));
+	}
+
+	private function default_logger(int $level, string $message) {
+		global $config;
+
+		if (isset($config['syslog']) && $config['syslog']) {
+			_syslog($level, $message);
+		} else {
+			\error_log($message);
+		}
+	}
+
+	public function __construct() {
+		$this->include_details = self::isCli();
+		$this->logger_fn = [ __CLASS__, 'default_logger' ];
+	}
+
+	public function setIncludeDetails(bool $include_details) {
+		$this->include_details = $include_details;
+	}
+
+	public function setLogger(?callable $logger_fn) {
+		$this->logger_fn = $logger_fn !== null ? $logger_fn : [ __CLASS__, 'default_logger' ];
+	}
+
+	public function installGlobally() {
+		$logger_fn = $this->logger_fn;
+		$include_details = $this->include_details || self::isCli();
+
+		\set_error_handler(function($errno, $errstr, $errfile, $errline) use ($logger_fn, $include_details) {
+			$errno = \error_reporting() & $errno;
+			if ($errno !== 0) {
+				$level = self::errnoToLogLevel($errno);
+
+				// https://stackoverflow.com/a/35930682
+				$e = new \Exception();
+				$trace_str = $e->getTraceAsString();
+				$trace = $e->getTrace();
+				self::handle_error($level, $errstr, $logger_fn, $include_details, $errfile, $errline, $trace_str, $trace);
+			}
+			return false;
+		});
+
+		\set_exception_handler(function($exception) use ($logger_fn, $include_details) {
+			$message = $exception->getMessage();
+			$file = $exception->getFile();
+			$line = $exception->getLine();
+			$trace_str = $exception->getTraceAsString();
+			$trace = $exception->getTrace();
+
+			self::handle_error(\LOG_EMERG, $message, $logger_fn, $include_details, $file, $line, $trace_str, $trace);
+		});
+
+		\register_shutdown_function(function() use ($logger_fn, $include_details) {
+			$error = \error_get_last();
+			if ($error !== null) {
+				$level = self::errnoToLogLevel($error['type']);
+				$message = $error['message'];
+				$file = $error['file'];
+				$line = $error['line'];
+
+				self::handle_error($level, $message, $logger_fn, $include_details, $file, $line, '<UNAVAILABLE>', []);
+			}
+		});
+	}
+}
+
+/**
+ * Install a fancy error handler with the given logger.
+ *
+ * @param ?callable $logger Called when there is to log something. Use null to use the minimal default implementation.
+ *                          The callable is invoke with two parameters, the first being the log level (integer), as
+ *                          listed by the syslog constants, the second is the log message (string).
+ *                          Consider that $config may not have been initialized yet.
+ */
+function install_error_handler(bool $basic, ?callable $logger_fn): void {
+	global $config;
+
+	$logger_fn ??= function($level, $message) use ($config) {
+		if (isset($config['syslog']) && $config['syslog']) {
+			_syslog($level, $message);
+		} else {
+			\error_log($message);
+		}
+	};
+
+	if (!$basic) {
+		\set_error_handler(function($errno, $errstr, $errfile, $errline) use ($config) {
+			if (\error_reporting() & $errno) {
+				$config['debug'] = true;
+				\error("$errstr in $errfile at line $errline");
+			}
+			return false;
+		});
 	}
 	return false;
 }
@@ -87,7 +300,7 @@ function error($message, $priority = true, $debug_stuff = false) {
 			'message' => $message,
 			'mod' => $mod,
 			'board' => isset($board) ? $board : false,
-			'debug' => str_replace("\n", '&#10;', utf8tohtml(print_r($debug_stuff, true)))
+			'debug' => \str_replace("\n", '&#10;', utf8tohtml(\print_r($debug_stuff, true)))
 		))
 	]));
 }