Question

In my PHP web application, I want to have the ability to perform the following logging operations:

1. Write a database record to an ‘error_log’ table.
2. Write a database record to a ‘history_log’ table.
3. Log all queries to the Firebug console via FirePHP.
4. Log any arbitrary data to the Firebug console using FirePHP.

I am trying to decide on the better achitecture. I have two in mind. Which of these is the better one? I’m open to others as well.

Design #1

• abstract class Logger
  • class FirebugConsoleLogger
    • getInstance()
    • log(string)
  • class DatabaseLogger
    • getInstance()
    • logError(logTypeId, affiliateId, detailsArray)
    • logHistory(logTypeId, affiliateId, detailsArray)

Design #2

• class Logger
• getInstance()
• logToFirebugConsole(string)
• logError(string)
• logHistory(string)

EDIT Here’s what I’m probably going to go with.

• class FirebugConsoleLogger
  • public getInstance()
  • public log(string)
• abstract class Logger
  • abstract public log(typeId, affiliateId, details)
  • class ErrorLogger
    • public getInstance()
    • public log(typeId, affiliateId, details)
  • class HistoryLogger
    • public getInstance()
    • public log(typeId, affiliateId, details)

Answer 1

I would use neither. I’d use a design that implements the same log method for each implementation. So it looks like Design #1, but a little different.

• abstract class Logger
  • log(string)

Create descendants for each type of log you have and override the log method.

Then, create a factory for specific purposes, so:

• class QueryLoggerFactory
  • getInstance() // Returns a/the FireBugConsoleLogger instance
• class ErrorLoggerFactory
  • getInstance() // Returns a database logger instance
• class HistoryLoggerFactory
  • getInstance() // Returns same or different database logger instance

That way, when you need to log a query, you just call

QueryLoggerFactory->getInstance()->log($query);

And nowhere in your application you need to call a specific method. If you decide you want to store the query in the database too, you just instantiate a different logger in your factory. You can even instantiate a logger that logs itself to two other loggers, so you can store errors in FireBug and in the database. Or you can instantiate a void logger that doesn’t log anything.