Advanced error handling in PHP

Dumper.php

<?php /****************** vi: set fenc=utf-8 ts=4 sw=4 et: *****************
 *
 *   Copyright : (C) 2011 Nicolas Grekas. All rights reserved.
 *   Email     : p@tchwork.org
 *   License   : http://www.gnu.org/licenses/lgpl.txt GNU/LGPL
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 ***************************************************************************/

namespace Patchwork\PHP;

/**
 * Dumper extends Walker and adds managing depth and length limits, alongside with
 * a callback mechanism for getting detailed information about objects and resources.
 *
 * For example and by default, resources of type stream are expanded by stream_get_meta_data,
 * those of type process by proc_get_status, and closures are associated with a method that
 * uses reflection to provide detailed information about anonymous functions. This class is
 * designed to implement these mechanisms in a way independent of the final representation.
 */
abstract class Dumper extends Walker
{
    public

    $maxLength = 100,
    $maxDepth = 10;

    protected

    $depthLimited = array(),
    $reserved = array('_' => 1, '__cutBy' => 1, '__refs' => 1, '__proto__' => 1),
    $callbacks = array(
        'o:closure' => array(__CLASS__, 'castClosure'),
        'r:stream' => 'stream_get_meta_data',
        'r:process' => 'proc_get_status',
    );


    function setCallback($type, $callback)
    {
        $this->callbacks[strtolower($type)] = $callback;
    }

    protected function dumpObject($obj)
    {
        $c = get_class($obj);
        $p = array($c => $c)
            + class_parents($obj)
            + class_implements($obj)
            + array('*' => '*');

        foreach ($p as $p)
        {
            if (isset($this->callbacks[$p = 'o:' . strtolower($p)]))
            {
                if (!$p = $this->callbacks[$p]) $a = array();
                else
                {
                    try {$a = call_user_func($p, $obj);}
                    catch (\Exception $e) {unset($a); continue;}
                }
                break;
            }
        }

        isset($a) || $a = (array) $obj;

        $this->walkHash($c, $a);
    }

    protected function dumpResource($res)
    {
        $h = get_resource_type($res);

        if (empty($this->callbacks['r:' . $h])) $res = array();
        else
        {
            try {$res = call_user_func($this->callbacks['r:' . $h], $res);}
            catch (\Exception $e) {$res = array();}
        }

        $this->walkHash("resource:{$h}", $res);
    }

    protected function dumpRef($is_soft, $ref_counter = null, &$ref_value = null)
    {
        if (null !== $ref_value && isset($this->depthLimited[$ref_counter]) && $this->depth !== $this->maxDepth)
        {
            unset($this->depthLimited[$ref_counter]);

            switch (true)
            {
            case is_resource($ref_value): $this->dumpResource($ref_value); return true;
            case is_object($ref_value): $this->dumpObject($ref_value); return true;
            case is_array($ref_value):
                $ref_counter = count($ref_value);
                isset($ref_value[$this->token]) && --$ref_counter;
                $this->walkHash('array:' . $ref_counter, $ref_value);
                return true;
            }
        }

        return false;
    }

    protected function walkHash($type, &$a)
    {
        $len = count($a);
        isset($a[$this->token]) && --$len;

        if ($len && $this->depth === $this->maxDepth && 0 < $this->maxDepth)
        {
            $this->depthLimited[$this->counter] = 1;

            if (isset($this->refPool[$this->counter]))
                $this->refPool[$this->counter]['ref_counter'] = $this->counter;

            $this->dumpString('__cutBy', true);
            $this->dumpScalar($len);
            $len = 0;
        }

        if (!$len) return array();

        $i = 0;
        ++$this->depth;
        if (false !== strpos($type, ':')) unset($type);

        foreach ($a as $k => &$a)
        {
            if ($k === $this->token) continue;
            else if ($i === $this->maxLength && 0 < $this->maxLength)
            {
                if ($len -= $i)
                {
                    $this->dumpString('__cutBy', true);
                    $this->dumpScalar($len);
                }

                break;
            }
            else if (isset($type, $k[0]) && "\0" === $k[0]) $k = implode(':', explode("\0", substr($k, 1), 2));
            else if (isset($this->reserved[$k]) || false !== strpos($k, ':')) $k = ':' . $k;

            $this->dumpString($k, true);
            $this->walkRef($a);
            ++$i;
        }

        if (--$this->depth) return array();
        else return $this->cleanRefPools();
    }

    static function castClosure($c)
    {
        $a = array();
        if (!class_exists('ReflectionFunction', false)) return $a;
        $c = new \ReflectionFunction($c);
        $c->returnsReference() && $a[] = '&';

        foreach ($c->getParameters() as $p)
        {
            $n = ($p->isPassedByReference() ? '&$' : '$') . $p->getName();

            if ($p->isDefaultValueAvailable()) $a[$n] = $p->getDefaultValue();
            else $a[] = $n;
        }

        $a['use'] = array();

        if (false === $a['file'] = $c->getFileName()) unset($a['file']);
        else $a['lines'] = $c->getStartLine() . '-' . $c->getEndLine();

        if (!$c = $c->getStaticVariables()) unset($a['use']);
        else foreach ($c as $p => &$c) $a['use']['$' . $p] =& $c;

        return $a;
    }
}

ErrorHandler.php

<?php /****************** vi: set fenc=utf-8 ts=4 sw=4 et: *****************
 *
 *   Copyright : (C) 2011 Nicolas Grekas. All rights reserved.
 *   Email     : p@tchwork.org
 *   License   : http://www.gnu.org/licenses/lgpl.txt GNU/LGPL
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 ***************************************************************************/

namespace Patchwork\PHP;

/**
 * ErrorHandler is a tunable error and exception handler.
 *
 * It provides four bit fields that control how errors are handled:
 * - scream: never silenced errors
 * - recoverableErrors: errors not logged but throwing a RecoverableErrorException
 * - scopedErrors: errors logged with their local scope
 * - tracedErrors: errors logged with their trace, but only once for repeated errors
 *
 * Errors are logged with a Logger object by default, but any logger can be injected
 * provided it has the right interface. Errors are logged to the same file where non
 * catchable errors are written by PHP. Silenced non catchable errors that can be
 * detected at shutdown time are logged when the scream bit field allows so.
 *
 * Uncaught exceptions are turned to E_ERROR.
 *
 * As errors have a performance cost, repeated errors are all logged, so that the developper
 * can see them and weight them as more important to fix than others of the same level.
 */
class ErrorHandler
{
    public

    $scream = 0x51, // E_ERROR | E_CORE_ERROR | E_COMPILE_ERROR
    $recoverableErrors = 0x1100, // E_RECOVERABLE_ERROR | E_USER_ERROR
    $scopedErrors = 0x0203, // E_ERROR | E_WARNING | E_USER_WARNING
    $tracedErrors = 0x1302; // E_RECOVERABLE_ERROR | E_USER_ERROR | E_WARNING | E_USER_WARNING

    protected

    $logger,
    $loggedTraces = array(),
    $registeredErrors = 0;

    protected static

    $logFile,
    $logStream,
    $shuttingDown = 0,
    $handlers = array();


    static function start($log_file = 'php://stderr', self $handler = null)
    {
        null === $handler && $handler = new self;

        // See also http://php.net/error_reporting
        // Formatting errors with html_errors, error_prepend_string or
        // error_append_string only works with displayed errors, not logged ones.
        ini_set('display_errors', false);
        ini_set('log_errors', true);
        ini_set('error_log', $log_file);

        // Some fatal errors can be caught at shutdown time!
        // Then, any fatal error is really fatal: remaining shutdown
        // functions, output buffering handlers or destructors are not called!
        register_shutdown_function(array(__CLASS__, 'shutdown'));

        self::$logFile = $log_file;

        // Register the handler and top it to the current error_reporting() level
        $handler->register(error_reporting());

        return $handler;
    }

    static function getHandler()
    {
        return end(self::$handlers);
    }

    static function shutdown()
    {
        self::$shuttingDown = 1;

        if (false === $handler = end(self::$handlers)) return;

        if ($e = self::getLastError())
        {
            switch ($e['type'])
            {
            // Get the last uncatchable error
            case E_ERROR: case E_PARSE:
            case E_CORE_ERROR: case E_CORE_WARNING:
            case E_COMPILE_ERROR: case E_COMPILE_WARNING:
                $handler->handleLastError($e);
                self::resetLastError();
            }
        }
    }

    static function getLastError()
    {
        $e = error_get_last();
        return empty($e['message']) ? false : $e;
    }

    static function resetLastError()
    {
        // Reset error_get_last() by triggering a silenced empty user notice
        set_error_handler(array(__CLASS__, 'falseError'));
        $r = error_reporting(81);
        user_error('', E_USER_NOTICE);
        error_reporting($r);
        restore_error_handler();
    }

    static function falseError()
    {
        return false;
    }


    function register($error_types = -1)
    {
        $this->registeredErrors = $error_types;
        set_exception_handler(array($this, 'handleException'));
        set_error_handler(array($this, 'handleError'), $error_types);
        self::$handlers[] = $this;
    }

    function unregister()
    {
        $ok = array(
            $this === end(self::$handlers),
            array($this, 'handleError') === set_error_handler(array(__CLASS__, 'falseError')),
            array($this, 'handleException') === set_exception_handler(array(__CLASS__, 'falseError')),
        );

        if ($ok = array(true, true, true) === $ok)
        {
            array_pop(self::$handlers);
            restore_error_handler();
            restore_exception_handler();
            $this->registeredErrors = 0;
        }
        else user_error('Failed to unregister: the current error or exception handler is not me', E_USER_WARNING);

        restore_error_handler();
        restore_exception_handler();

        return $ok;
    }

    function handleError($type, $message, $file, $line, $scope, $trace_offset = 0, $log_time = 0)
    {
        $throw = $this->recoverableErrors & $type;
        $log = error_reporting() & $type;

        if ($log || $throw || $scream = $this->scream & $type)
        {
            $log_time || $log_time = microtime(true);

            if ($throw)
            {
                // To prevent extra logging of caught RecoverableErrorException and
                // to remove logged and uncaught exception messages duplication and
                // to dismiss any cryptic "Exception thrown without a stack frame"
                // recoverable errors are logged but only at shutdown time.
                $throw = new RecoverableErrorException($message, 0, $type, $file, $line);
                $scream = self::$shuttingDown ? 1 : $log = 0;
            }

            if (0 <= $trace_offset)
            {
                ++$trace_offset;

                // For duplicate errors, log the trace only once
                $e = md5("{$type}/{$line}/{$file}\x00{$message}", true);

                if (!($this->tracedErrors & $type) || isset($this->loggedTraces[$e])) $trace_offset = -1;
                else if ($log) $this->loggedTraces[$e] = 1;
            }

            if ($log || $scream)
            {
                $e = compact('type', 'message', 'file', 'line');
                $e['level'] = $type . '/' . error_reporting();
                $line = 0; // Read $trace_args

                if ($log)
                {
                    if ($this->scopedErrors & $type)
                    {
                        null !== $scope && $e['scope'] = $scope;
                        0 <= $trace_offset && $e['trace'] = debug_backtrace(true); // DEBUG_BACKTRACE_PROVIDE_OBJECT
                        $line = 1;
                    }
                    else if ($throw && 0 <= $trace_offset) $e['trace'] = $throw->getTrace();
                    else if (0 <= $trace_offset) $e['trace'] = debug_backtrace(/*<*/PHP_VERSION_ID >= 50306 ? DEBUG_BACKTRACE_IGNORE_ARGS : false/*>*/);
                }

                $this->getLogger()->logError($e, $trace_offset, $line, $log_time);
            }

            if ($throw)
            {
                $throw->scope = $scope;
                $log || $throw->traceOffset = $trace_offset;
                throw $throw;
            }
        }

        return (bool) $log;
    }

    function handleException(\Exception $e, $log_time = 0)
    {
        $this->recoverableErrors &= ~E_ERROR; // Prevent any accidental rethrow
        $this->handleError(
            E_ERROR, "Uncaught exception '" . get_class($e) . "'",
            $e->getFile(), $e->getLine(),
            array('uncaught-exception' => $e),
            -1, $log_time
        );
    }

    function handleLastError($e)
    {
        // Handle errors when they have not been logged by the native PHP error handler.
        // If this is the first event, handle it also to log any context data with it.
        // Otherwise, do not duplicate it.
        if (isset($this->logger) && (error_reporting() & $e['type'])) return;
        call_user_func_array(array($this, 'handleError'), $e + array(null, -1));
    }

    function getLogger()
    {
        if (isset($this->logger)) return $this->logger;
        isset(self::$logStream) || self::$logStream = fopen(self::$logFile, 'ab');
        return $this->logger = new Logger(self::$logStream);
    }
}

class RecoverableErrorException extends \ErrorException implements RecoverableErrorInterface
{
    public $traceOffset = -1, $scope = array();
}

interface RecoverableErrorInterface {}

example.php

<?php

use Patchwork\PHP as p;

header('Content-type: text/plain');
error_reporting(E_ALL | E_STRICT);
ini_set('display_errors', true);

include 'Walker.php';
include 'Dumper.php';
include 'JsonDumper.php';
include 'Logger.php';
include 'ErrorHandler.php';

p\ErrorHandler::start('php://stderr')->getLogger()->log(
    'debug-start',
    array(
        'start-time' => date('c'),
        'request-context' => $_SERVER,
    )
);

register_shutdown_function('log_shutdown');

user_error('user triggered warning', E_USER_WARNING);
echo $a; // undefined variable
eval('a()'); // non-fatal parse error
@eval('a();'); // silenced undefined function fatal error

function log_shutdown()
{
    p\DebugLog::getHandler()->getLogger()->log('debug-shutdown', array(
        'response-headers' => headers_list(),
    ));
}

JsonDumper.php

<?php /****************** vi: set fenc=utf-8 ts=4 sw=4 et: *****************
 *
 *   Copyright : (C) 2011 Nicolas Grekas. All rights reserved.
 *   Email     : p@tchwork.org
 *   License   : http://www.gnu.org/licenses/lgpl.txt GNU/LGPL
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 ***************************************************************************/

namespace Patchwork\PHP;

/**
 * JsonDumper implements the JSON convention to dump any PHP variable with high accuracy.
 *
 * See https://github.com/nicolas-grekas/Patchwork-Doc/blob/master/Dumping-PHP-Data-en.md
 */
class JsonDumper extends Dumper
{
    public

    $maxString = 100000;

    protected

    $line = '',
    $lines = array(),
    $lastHash = 0;


    static function dump(&$a)
    {
        $d = new self;
        $d->setCallback('line', array($d, 'echoLine'));
        $d->walk($a);
    }

    static function get($a)
    {
        $d = new self;
        $d->setCallback('line', array($d, 'stackLine'));
        $d->walk($a);
        return implode("\n", $d->lines);
    }


    function walk(&$a)
    {
        $this->line = '';
        parent::walk($a);
        '' !== $this->line && $this->dumpLine(0);
    }

    protected function dumpLine($depth_offset)
    {
        call_user_func($this->callbacks['line'], $this->line, $this->depth + $depth_offset);
        $this->line = '';
    }

    protected function dumpRef($is_soft, $ref_counter = null, &$ref_value = null)
    {
        if (parent::dumpRef($is_soft, $ref_counter, $ref_value)) return;

        $is_soft = $is_soft ? 'r' : 'R';
        $this->line .= "\"{$is_soft}`{$this->counter}:{$ref_counter}\"";
    }

    protected function dumpScalar($a)
    {
        switch (true)
        {
        case null === $a: $this->line .= 'null'; break;
        case true === $a: $this->line .= 'true'; break;
        case false === $a: $this->line .= 'false'; break;
        case INF === $a: $this->line .= '"n`INF"'; break;
        case -INF === $a: $this->line .= '"n`-INF"'; break;
        case is_nan($a): $this->line .= '"n`NAN"'; break;
        case $a > 9007199254740992 && is_int($a): $a = '"n`' . $a . '"'; // JavaScript max integer is 2^53
        default: $this->line .= (string) $a; break;
        }
    }

    protected function dumpString($a, $is_key)
    {
        if ($is_key)
        {
            $is_key = $this->lastHash === $this->counter && !isset($this->depthLimited[$this->counter]);
            $this->dumpLine(-$is_key, $this->line .= ',');
            $is_key = ': ';
        }
        else $is_key = '';

        if ('' === $a) return $this->line .= '""' . $is_key;

        if (!preg_match("''u", $a)) $a = 'b`' . utf8_encode($a);
        else if (false !== strpos($a, '`')) $a = 'u`' . $a;

        if (0 < $this->maxString && $this->maxString < $len = iconv_strlen($a, 'UTF-8') - 1)
            $a = $len . ('`' !== substr($a, 1, 1) ? 'u`' : '') . substr($a, 0, $this->maxString + 1);

        $this->line .= '"' . str_replace(
            array(
                  '\\', '"', '</',
                  "\x00",  "\x01",  "\x02",  "\x03",  "\x04",  "\x05",  "\x06",  "\x07",
                  "\x08",  "\x09",  "\x0A",  "\x0B",  "\x0C",  "\x0D",  "\x0E",  "\x0F",
                  "\x10",  "\x11",  "\x12",  "\x13",  "\x14",  "\x15",  "\x16",  "\x17",
                  "\x18",  "\x19",  "\x1A",  "\x1B",  "\x1C",  "\x1D",  "\x1E",  "\x1F",
            ),
            array(
                '\\\\', '\\"', '<\\/',
                '\u0000','\u0001','\u0002','\u0003','\u0004','\u0005','\u0006','\u0007',
                '\b'    ,'\t'    ,'\n'    ,'\u000B','\f'    ,'\r'    ,'\u000E','\u000F',
                '\u0010','\u0011','\u0012','\u0013','\u0014','\u0015','\u0016','\u0017',
                '\u0018','\u0019','\u001A','\u001B','\u001C','\u001D','\u001E','\u001F',
            ),
            $a
        ) . '"' . $is_key;
    }

    protected function walkHash($type, &$a)
    {
        if ('array:0' === $type) $this->line .= '[]';
        else
        {
            $h = $this->lastHash;
            $this->line .= '{"_":';
            $this->lastHash = $this->counter;
            $this->dumpString($this->counter . ':' . $type, false);

            if ($type = parent::walkHash($type, $a))
            {
                ++$this->depth;
                $this->dumpString('__refs', true);
                $this->line .= '{';
                foreach ($type as $k => &$a) $a = '"' . $k . '":[' . implode(',', $a) . ']';
                $this->line .= implode(',', $type) . '}';
                --$this->depth;
            }

            if ($this->counter !== $this->lastHash || isset($this->depthLimited[$this->counter]))
                $this->dumpLine(1);

            $this->lastHash = $h;
            $this->line .= '}';
        }
    }


    static function echoLine($line, $depth)
    {
        echo str_repeat('  ', $depth), $line, "\n";
    }

    protected function stackLine($line, $depth)
    {
        $this->lines[] = str_repeat('  ', $depth) . $line;
    }
}

Logger.php

<?php /****************** vi: set fenc=utf-8 ts=4 sw=4 et: *****************
 *
 *   Copyright : (C) 2011 Nicolas Grekas. All rights reserved.
 *   Email     : p@tchwork.org
 *   License   : http://www.gnu.org/licenses/lgpl.txt GNU/LGPL
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 ***************************************************************************/

namespace Patchwork\PHP;

/**
 * Logger logs messages to an output stream.
 *
 * Messages just have a type and associated data. The dump format is handled by JsonDumper
 * which allows unprecedented accuracy for associated data representation.
 *
 * Error messages are handled specifically in order to make them more friendly,
 * especially for traces and exceptions.
 */
class Logger
{
    public

    $writeLock = true,
    $lineFormat = "%s\n",
    $loggedGlobals = array('_SERVER');

    protected

    $logStream,
    $prevTime = 0,
    $startTime = 0,
    $isFirstEvent = true;

    public static

    $errorTypes = array(
        E_RECOVERABLE_ERROR => 'E_RECOVERABLE_ERROR',
        E_DEPRECATED => 'E_DEPRECATED',
        E_USER_DEPRECATED => 'E_USER_DEPRECATED',
        E_ERROR => 'E_ERROR',
        E_WARNING => 'E_WARNING',
        E_PARSE => 'E_PARSE',
        E_NOTICE => 'E_NOTICE',
        E_CORE_ERROR => 'E_CORE_ERROR',
        E_CORE_WARNING => 'E_CORE_WARNING',
        E_COMPILE_ERROR => 'E_COMPILE_ERROR',
        E_COMPILE_WARNING => 'E_COMPILE_WARNING',
        E_USER_ERROR => 'E_USER_ERROR',
        E_USER_WARNING => 'E_USER_WARNING',
        E_USER_NOTICE => 'E_USER_NOTICE',
        E_STRICT => 'E_STRICT',
    );


    function __construct($log_stream, $start_time = 0)
    {
        $start_time || $start_time = microtime(true);
        $this->startTime = $this->prevTime = $start_time;
        $this->logStream = $log_stream;
    }

    function log($type, $data, $log_time = 0)
    {
        // Get time and memory profiling information

        $log_time || $log_time = microtime(true);

        $data = array(
            'time' => date('c', $log_time) . sprintf(
                ' %06dus - %0.3fms - %0.3fms',
                100000 * ($log_time - floor($log_time)),
                  1000 * ($log_time - $this->startTime),
                  1000 * ($log_time - $this->prevTime)
            ),
            'mem'  => memory_get_peak_usage(true) . ' - ' . memory_get_usage(true),
            'data' => $data,
        );

        if ($this->isFirstEvent && $this->loggedGlobals)
        {
            $data['globals'] = array();
            foreach ($this->loggedGlobals as $log_time)
                $data['globals'][$log_time] = isset($GLOBALS[$log_time]) ? $GLOBALS[$log_time] : null;
        }

        $this->writeLock && flock($this->logStream, LOCK_EX);
        $this->writeEvent($type, $data);
        $this->writeLock && flock($this->logStream, LOCK_UN);

        $this->prevTime = microtime(true);
        $this->isFirstEvent = false;
    }

    function logError($e, $trace_offset = -1, $trace_args = 0, $log_time = 0)
    {
        $e = array(
            'mesg' => $e['message'],
            'type' => self::$errorTypes[$e['type']] . ' ' . $e['file'] . ':' . $e['line'],
        ) + $e;

        unset($e['message'], $e['file'], $e['line']);
        if (0 > $trace_offset) unset($e['trace']);
        else if (!empty($e['trace'])) $e['trace'] = $this->filterTrace($e['trace'], $trace_offset, $trace_args);

        $this->log('php-error', $e, $log_time);
    }

    function castException($e)
    {
        $a = (array) $e;

        $a["\0Exception\0trace"] = $this->filterTrace($a["\0Exception\0trace"], $e instanceof RecoverableErrorInterface ? $e->traceOffset : 0, 1);
        if (null === $a["\0Exception\0trace"]) unset($a["\0Exception\0trace"]);
        if ($e instanceof RecoverableErrorInterface) unset($a['traceOffset']);
        if (empty($a["\0Exception\0previous"])) unset($a["\0Exception\0previous"]);
        if ($e instanceof \ErrorException && isset(self::$errorTypes[$a["\0*\0severity"]])) $a["\0*\0severity"] = self::$errorTypes[$a["\0*\0severity"]];
        unset($a["\0Exception\0string"], $a['xdebug_message'], $a['__destructorException']);

        return $a;
    }

    function filterTrace($trace, $offset, $args)
    {
        if (0 > $offset || empty($trace[$offset])) return null;
        else $t = $trace[$offset];

        if (empty($t['class']) && isset($t['function']))
            if ('user_error' === $t['function'] || 'trigger_error' === $t['function'])
                ++$offset;

        $offset && array_splice($trace, 0, $offset);

        foreach ($trace as &$t)
        {
            $t = array(
                'call' => (isset($t['class']) ? $t['class'] . $t['type'] : '')
                    . $t['function'] . '()'
                    . (isset($t['line']) ? " {$t['file']}:{$t['line']}" : '')
            ) + $t;

            unset($t['class'], $t['type'], $t['function'], $t['file'], $t['line']);
            if (isset($t['args']) && !$args) unset($t['args']);
        }

        return $trace;
    }

    function writeEvent($type, $data)
    {
        fprintf($this->logStream, $this->lineFormat, "*** {$type} ***");

        $d = new JsonDumper;
        $d->setCallback('line', array($this, 'writeLine'));
        $d->setCallback('o:exception', array($this, 'castException'));
        $d->walk($data);

        fprintf($this->logStream, $this->lineFormat, '***');
    }

    function writeLine($line, $depth)
    {
        fprintf($this->logStream, $this->lineFormat, str_repeat('  ', $depth) . $line);
    }
}

Walker.php

<?php /****************** vi: set fenc=utf-8 ts=4 sw=4 et: *****************
 *
 *   Copyright : (C) 2011 Nicolas Grekas. All rights reserved.
 *   Email     : p@tchwork.org
 *   License   : http://www.gnu.org/licenses/lgpl.txt GNU/LGPL
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 ***************************************************************************/

namespace Patchwork\PHP;

/**
 * Walker implements a mechanism to generically traverse any PHP variable.
 *
 * It takes internal references into account, recursive or non-recursive, without preempting any
 * special use of the discovered data. It exposes only one public method ->walk(), which triggers
 * the traversal. It also has a public property ->checkInternalRefs set to true by default, to
 * disable the check for internal references if the mechanism is considered too expensive.
 * Checking recursive references and object/resource can not be disabled but is much lighter.
 */
abstract class Walker
{
    public

    $checkInternalRefs = true;

    protected

    $tag,
    $token,
    $depth = 0,
    $counter = 0,
    $arrayType = 0,
    $refMap = array(),
    $refPool = array(),
    $valPool = array(),
    $objPool = array(),
    $arrayPool = array();


    abstract protected function dumpRef($is_soft, $ref_counter = null, &$ref_value = null);
    abstract protected function dumpScalar($val);
    abstract protected function dumpString($str, $is_key);
    abstract protected function dumpObject($obj);
    abstract protected function dumpResource($res);


    function walk(&$a)
    {
        $this->tag = (object) array();
        $this->token = md5(mt_rand() . spl_object_hash($this->tag), true);
        $this->tag = array($this->token => $this->tag);
        $this->counter = $this->depth = 0;
        $this->walkRef($a);
    }

    protected function walkRef(&$a)
    {
        ++$this->counter;

        if (is_array($a)) return $this->walkArray($a);

        $v = $a;

        if ($this->checkInternalRefs && 1 < $this->counter)
        {
            $this->refPool[$this->counter] =& $a;
            $this->valPool[$this->counter] = $a;
            $a = $this->tag;
        }

        switch (true)
        {
        default: $this->dumpScalar($v); break;
        case is_string($v): $this->dumpString($v, false); break;

        case is_object($v): $h = pack('H*', spl_object_hash($v)); // no break;
        case is_resource($v): isset($h) || $h = (int) substr((string) $v, 13);

            if (empty($this->objPool[$h])) $this->objPool[$h] = $this->counter;
            else return $this->dumpRef(true, $this->refMap[$this->counter] = $this->objPool[$h], $v);

            $t = $this->arrayType;
            $this->arrayType = 0;
            if (isset($h[0])) $this->dumpObject($v);
            else $this->dumpResource($v);
            $this->arrayType = $t;
        }
    }

    protected function walkArray(&$a)
    {
        if (isset($a[$this->token]))
        {
            if ($this->tag[$this->token] === $c = $a[$this->token])
            {
                if (empty($a['ref_counter']))
                {
                    $a[] = -$this->counter;
                    return $this->dumpRef(false);
                }

                $c = $a['ref_counter'];
                unset($a);
                $a = $this->valPool[$c];
            }

            $this->refMap[-$this->counter] = $c;
            return $this->dumpRef(false, $c, $a);
        }

        if ($this->checkInternalRefs) $token = $this->token;
        else
        {
/**/        if (PHP_VERSION_ID >= 50206)
/**/        {
                if (0 === $this->arrayType)
                {
                    // Detect recursive arrays by catching recursive count warnings
                    $this->arrayType = 1;
                    set_error_handler(array($this, 'catchRecursionWarning'));
                    count($a, COUNT_RECURSIVE);
                    restore_error_handler();
                }
                if (2 === $this->arrayType) $token = $this->token;
/**/        }
/**/        else
/**/        {
                $token = $this->token;
/**/        }
        }

        $len = count($a);

        if (isset($token))
        {
            $a[$token] = $this->counter;
            $this->arrayPool[] =& $a;
        }

        $this->walkHash('array:' . $len, $a);
    }

    protected function walkHash($type, &$a)
    {
        ++$this->depth;

        foreach ($a as $k => &$a)
        {
            if ($k === $this->token) continue;
            $this->dumpString($k, true);
            $this->walkRef($a);
        }

        if (--$this->depth) return array();
        else return $this->cleanRefPools();
    }

    protected function cleanRefPools()
    {
        $refs = array();

        foreach ($this->refPool as $k => &$v)
        {
            $len = $v;
            $v = $this->valPool[$k];
            if (isset($len[0]))
            {
                unset($len['ref_counter']);
                $refs[$k] = array_slice($len, 1);
            }
        }

        $this->refPool = $this->valPool = $this->objPool = array();
        foreach ($this->refMap as $len => $k) $refs[$k][] = $len;
        foreach ($this->arrayPool as &$a) unset($a[$this->token]);
        $this->arrayPool = $this->refMap = array();

        return $refs;
    }

    protected function catchRecursionWarning()
    {
        $this->arrayType = 2;
    }
}