Awesome

Patchwork Error Logger: Advanced PHP error handling and high accuracy JSON logging

Here are five PHP classes under Apache 2 and GPLv2 licenses, focused on particular aspects of errors handling in PHP. Together, they offer unprecedented accuracy for logging what's going on with the internal state of your applications.

For interoperability and readability, errors and variables' states are logged to JSON.

Error handling

Patchwork\PHP\ErrorHandler

is a flexible error and exception handler.

Its default behavior is to log errors to the same file where fatal errors are written. That way, the same debug stream contains both uncatchable fatal errors and catchable ones in an easy to parse format.

Each error type is handled according to four bit fields:

• scream: controls which errors are never @-silenced - silenced fatal errors that can be detected at shutdown time are logged when the bit field allows so,
• thrownErrors: controls which errors are turned to exceptions (defaults to E_RECOVERABLE_ERROR | E_USER_ERROR),
• scopedErrors: controls which errors are logged along with their local context,
• tracedErrors: controls which errors are logged along with their trace (but only once for repeated errors).

Since errors, even silenced ones, always 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 type.

High accuracy logging

Did you try to dump a variable inside an output buffering handler? Any error handling or variable logging code out there using either ob_start(), print_r() or var_dump() fails in this situation. Neither serialize() is usable, because some objects throw an exception when serialized. If your current dumper uses json_encode() internally (or var_export() since PHP 5.3.3) then you may be safe. But even then, you won't be able to log intra-references in your arrays/objects, nor details for resources and so on.

Because errors always happen in unexpected situations, a robust logger must work whatever the running context is, for any variable type.

In order to allow a higher level of accuracy, variables are logged following the JSON convention to dump any PHP variable with high accuracy.

To achieve this, several classes are involved:

Patchwork\PHP\Logger

logs any message to an output stream.

Error messages are handled specifically in order to make them more friendly, especially for traces and exceptions.

Logged messages just have to have a type and some associated data. They are sent to a JsonDumper object who writes to your debug stream (but that can be any other destination).

Patchwork\PHP\JsonDumper

implements the JSON convention to dump any PHP variable with high accuracy.

It extends the Dumper class.

Patchwork\PHP\Dumper

Handles a callback mechanism for getting detailed information about dumped objects and resources, alongside with managing depth and length limits.

It extends the Walker class.

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.

Usage

Including the bootup.logger.php file is the easiest way to start with these features. By defaults, errors are written to php://stderr, but the file is here to be tuned by you.

This code is extracted from the Patchwork framework where it serves as the foundation for the debugging system. It is released here standalone in the hope that it can be used in a different context successfully!