title: PHP Static Methods/Singleton Pattern
body: <p>I am designing a new architecture for my company's software product.  I am fairly new to unit testing.  I read some horror stories about the use of singleton and static methods, but I am not clearly understanding the problem with using them and would appreciate some enlightenment.</p>
  
  <p>Here is what I am doing:</p>
  
  <p>I have a multi-tier architecture.  At the server side level, I am using a series of reusable objects to represent database tables, called "Handlers".  These handlers use other objects, like XMLObjects, XMLTables, different Datastructures, etc.  Most of these are homemade, not your prepacked objects.  Anyway, on top of this layer is a pseudo-singleton layer.  The primary purpose of this is to simplify higher levels of server side code and create seamless class management.  I can say:</p>
  
  <pre><code>$tablehandler = databasename::Handler('tablename') 
  </code></pre>
  
  <p>...to get a table.  I don't see the inherent problem with this.  I am using a stack of handlers (an associative array) to contain instances of the different objects.  I am not using globals, and all static datamembers are protected or private.  My question is how this can cause problems with unit testing.  I am not looking for bandwagon rhetoric, I am looking for a causal relationship.  I would also appreciate any other insight to this.  I feel like its an extremely flexible and efficient architecture at this point.  Any help here would be great.</p>