2.0.0-beta2

• BC Break: This is a major release, see UPGRADE.md and the 2.0.0-beta1 changelog for details if you are coming from a 1.x release
• BC Break: PHP 7.2 is now the minimum required PHP version.
• BC Break: Removed SlackbotHandler, RavenHandler and HipChatHandler, see UPGRADE.md for details
• Added OverflowHandler which will only flush log records to its nested handler when reaching a certain amount of logs (i.e. only pass through when things go really bad)
• Added TelegramBotHandler to log records to a Telegram bot account
• Added support for JsonSerializable when normalizing exceptions
• Added support for RFC3164 (outdated BSD syslog protocol) to SyslogUdpHandler
• Added SoapFault details to formatted exceptions
• Fixed DeduplicationHandler silently failing to start when file could not be opened
• Fixed issue in GroupHandler and WhatFailureGroupHandler where setting multiple processors would duplicate records
• Fixed GelfFormatter losing some data when one attachment was too long
• Fixed issue in SignalHandler restarting syscalls functionality
• Improved performance of LogglyHandler when sending multiple logs in a single request

2.0.0-beta1

• BC Break: This is a major release, see UPGRADE.md for details if you are coming from a 1.x release
• BC Break: PHP 7.1 is now the minimum required PHP version.
• BC Break: Quite a few interface changes, only relevant if you implemented your own handlers/processors/formatters
• BC Break: Removed non-PSR-3 methods to add records, all the add* (e.g. addWarning) methods as well as emerg, crit, err and warn
• BC Break: The record timezone is now set per Logger instance and not statically anymore
• BC Break: There is no more default handler configured on empty Logger instances
• BC Break: ElasticSearchHandler renamed to ElasticaHandler
• BC Break: Various handler-specific breaks, see UPGRADE.md for details
• Added scalar type hints and return hints in all the places it was possible. Switched strict_types on for more reliability.
• Added DateTimeImmutable support, all record datetime are now immutable, and will toString/json serialize with the correct date format, including microseconds (unless disabled)
• Added timezone and microseconds to the default date format
• Added SendGridHandler to use the SendGrid API to send emails
• Added LogmaticHandler to use the Logmatic.io API to store log records
• Added SqsHandler to send log records to an AWS SQS queue
• Added ElasticsearchHandler to send records via the official ES library. Elastica users should now use ElasticaHandler instead of ElasticSearchHandler
• Added NoopHandler which is similar to the NullHandle but does not prevent the bubbling of log records to handlers further down the configuration, useful for temporarily disabling a handler in configuration files
• Added ProcessHandler to write log output to the STDIN of a given process
• Added HostnameProcessor that adds the machine's hostname to log records
• Added a $dateFormat option to the PsrLogMessageProcessor which lets you format DateTime instances nicely
• Added support for the PHP 7.x mongodb extension in the MongoDBHandler
• Fixed many minor issues in various handlers, and probably added a few regressions too

1.24.0

• BC Notice: If you are extending any of the Monolog's Formatters' normalize method, make sure you add the new $depth = 0 argument to your function signature to avoid strict PHP warnings. See #808 for more details.
• Added a ResettableInterface in order to reset/reset/clear/flush handlers and processors
• Added a ProcessorInterface as an optional way to label a class as being a processor (mostly useful for autowiring dependency containers)
• Added a way to log signals being received using Monolog\SignalHandler
• Added ability to customize error handling at the Logger level using Logger::setExceptionHandler
• Added InsightOpsHandler to migrate users of the LogEntriesHandler
• Added protection to NormalizerFormatter against circular and very deep structures, it now stops normalizing at a depth of 9
• Added capture of stack traces to ErrorHandler when logging PHP errors
• Added RavenHandler support for a contexts context or extra key to forward that to Sentry's contexts
• Added forwarding of context info to FluentdFormatter
• Added SocketHandler::setChunkSize to override the default chunk size in case you must send large log lines to rsyslog for example
• Added ability to extend/override BrowserConsoleHandler
• Added SlackWebhookHandler::getWebhookUrl and SlackHandler::getToken to enable class extensibility
• Added SwiftMailerHandler::getSubjectFormatter to enable class extensibility
• Dropped official support for HHVM in test builds
• Fixed normalization of exception traces when call_user_func is used to avoid serializing objects and the data they contain
• Fixed naming of fields in Slack handler, all field names are now capitalized in all cases
• Fixed HipChatHandler bug where slack dropped messages randomly
• Fixed normalization of objects in Slack handlers
• Fixed support for PHP7's Throwable in NewRelicHandler
• Fixed race bug when StreamHandler sometimes incorrectly reported it failed to create a directory
• Fixed table row styling issues in HtmlFormatter
• Fixed RavenHandler dropping the message when logging exception
• Fixed WhatFailureGroupHandler skipping processors when using handleBatch
  and implement it where possible
• Fixed display of anonymous class names

1.23.0

• Improved SyslogUdpHandler's support for RFC5424 and added optional $ident argument
• Fixed GelfHandler truncation to be per field and not per message
• Fixed compatibility issue with PHP <5.3.6
• Fixed support for headless Chrome in ChromePHPHandler
• Fixed support for latest Aws SDK in DynamoDbHandler
• Fixed support for SwiftMailer 6.0+ in SwiftMailerHandler

1.22.1

• Fixed lots of minor issues in the new Slack integrations
• Fixed support for allowInlineLineBreaks in LineFormatter when formatting exception backtraces

1.22.0

• Added SlackbotHandler and SlackWebhookHandler to set up Slack integration more easily
• Added MercurialProcessor to add mercurial revision and branch names to log records
• Added support for AWS SDK v3 in DynamoDbHandler
• Fixed fatal errors occuring when normalizing generators that have been fully consumed
• Fixed RollbarHandler to include a level (rollbar level), monolog_level (original name), channel and datetime (unix)
• Fixed RollbarHandler not flushing records automatically, calling close() explicitly is not necessary anymore
• Fixed SyslogUdpHandler to avoid sending empty frames
• Fixed a few PHP 7.0 and 7.1 compatibility issues

1.21.0

• Break: Reverted the addition of $context when the ErrorHandler handles regular php errors from 1.20.0 as it was causing issues
• Added support for more formats in RotatingFileHandler::setFilenameFormat as long as they have Y, m and d in order
• Added ability to format the main line of text the SlackHandler sends by explictly setting a formatter on the handler
• Added information about SoapFault instances in NormalizerFormatter
• Added $handleOnlyReportedErrors option on ErrorHandler::registerErrorHandler (default true) to allow logging of all errors no matter the error_reporting level

1.20.0

• Added FingersCrossedHandler::activate() to manually trigger the handler regardless of the activation policy
• Added StreamHandler::getUrl to retrieve the stream's URL
• Added ability to override addRow/addTitle in HtmlFormatter
• Added the $context to context information when the ErrorHandler handles a regular php error
• Deprecated RotatingFileHandler::setFilenameFormat to only support 3 formats: Y, Y-m and Y-m-d
• Fixed WhatFailureGroupHandler to work with PHP7 throwables
• Fixed a few minor bugs

1.19.0

• Break: StreamHandler will not close streams automatically that it does not own. If you pass in a stream (not a path/url), then it will not close it for you. You can retrieve those using getStream() if needed
• Added DeduplicationHandler to remove duplicate records from notifications across multiple requests, useful for email or other notifications on errors
• Added ability to use %message% and other LineFormatter replacements in the subject line of emails sent with NativeMailHandler and SwiftMailerHandler
• Fixed HipChatHandler handling of long messages

1.18.2

• Fixed ElasticaFormatter to use more precise dates
• Fixed GelfMessageFormatter sending too long messages