Logger

Logger is a simple yet configurable logger for PHP. It is an opinionated implementation of PSR-3 Logger Interface. It uses classes called handlers to handle messages to log. Currently there is only one handler: StreamHandler which allows for logging to files or to streams such as php://stdout or php://stderr. Handlers can be easily written and plugged into Logger.

Opinionated?

This library attempts what we're calling an "opinionated" implementation of PSR-3. This is because while it successfully implements Psr\Log\LoggerInterface Logger deviates from the true spirit of the specification in various ways:

1. In section 1.1 PSR-3 states that when calling the log method with one of the log level constants (later shown to be in Psr\Log\LogLevel) it must have the same result as calling the level-specific methods. The log level constants in Psr\Log\LogLevel are strings, but the $level parameter of the log method in Psr\Log\LoggerInterface is typeless. The words of the specification suggest that the $level parameter should be a string, but the actual code implementors are to use doesn't specify a type. The same section also references RFC 5424 when mentioning the log level methods, but why use strings when there are standardized integers used to identify severity? Since the interface allows for any type for $level, Logger will prefer the actual RFC standard's integers but will accept and convert PSR-3's strings internally to the integers just so it can remain PSR-3 compatible.

2. In section 1.2 of the specification it describes an optional feature, placeholders, and requires the implementor to write code to parse out and replace placeholders using a syntax and a method that's not present anywhere else in the entirety of PHP. Logger won't support this feature because a logging library's place is to log messages and not to interpolate template strings. A separate library or a built-in function such as sprintf should be used instead. Logger provides a way to transform messages that can be used to hook in a preferred interpolation method if desired, though.

3. The specification in section 1.3 also specifies that if an Exception object is passed in the $context parameter it must be within an exception key. This makes sense, but curiously there's nary a mention of what to do with an Error object. They've existed since PHP 7 and can be thrown just like exceptions. Logger will accept any Throwable in the exception key, but at present does nothing with it. Theoretically future handlers could be written to take advantage of it for structured data.