Professional PHP Design Patterns

5.2. UML

The following Unified Modified Language (UML) diagram details a class design using the Data Access Object Design Pattern (see Figure 5-1) and is further explained in the following list:

Figure 5-1. Figure 5-1

• The BaseDAO class is an abstract class that the tableNameDAO class extends. BaseDAO has a private method to connect to the data source named connectToDB(). This stores the connection in the private instance variable dbConnection. BaseDAO contains two public methods, named fetch() and update().

• The fetch() method expects to receive a parameter called keyItem. This references the primary identifier of the data source that is expected to be returned. This method will perform the proper database calls and return the result set.

• The update() method expects to receive a parameter called keyedUpdateObject. This is an object or array that contains keys and values to update the database with. In this function, the columns and values are extracted and the update is applied.

• The tableNameDAO class directly correlates to a table in the database. The tableName variable stores the exact table name. This private variable is used to create the database calls in fetch() and update(). As an example of additional features that a Data Access Object can possess distinct from the base object, the searchBySpecificKey() function is diagramed. This method expects to receive a variable named ...