Inheritance

phpDocumentor is capable of inheriting a large amount of information from elements in superclasses and super-interfaces that have been overridden and in the case of classes and interfaces even from a superclass itself.

For ease of reading this document has been separated into three parts:

• Classes and interfaces
• Properties
• Methods

In each of these chapters we will describe how information is inherited for that specific element. If you read carefully then you will notice that they differ little, mostly varying in which tags are inherited and how each tag is influenced by a super-element.

Important

Interfaces and classes are treated equally with regards to inheritance, as such whenever we refer to a class we also mean an interface to make the text easier on the eyes.

The inheritDoc tag

Before we discuss how the documentation for each element is inherited it is interesting to point out the inheritDoc tag. The inline tag {@inheritDoc} is used in a description to import the description of a parent element, even if the child element already has a description.

So let us look at an example. In the following code block we re-define (override) a method of an imaginary superclass:

/**
 * This is the summary.
 *
 * This is the description specific to the redefined method. {@inheritDoc} And this is another
 * part specific to the redefined method.
 */
public function aMethod()
{
}

Now suppose that the overridden method has the description This is the description specific to the overridden method.; the description of the re-defined method will be:

This is the description specific to the redefined method. This is the description specific to the overridden
method. And this is another part specific to the redefined method.

As you can see, the two descriptions have been combined into one, where the overridden element’s description has been inserted in the location of the {@inheritDoc} inline tag.

Important

Currently some applications have DocBlocks containing just the {@inheritDoc} inline tag to indicate that their complete contents should be inherited. This usage breaks with the PHPDoc Standard as summaries cannot contain inline tags and inheritance is automatic; you do not need to define a special tag for it.

However, it does make clear that an element has been explicitly documented (and thus not forgotten). As such we are working to include a new (normal) tag in the PHPDoc Standard @inheritDoc that will serve that purpose.

Classes and interfaces

Perhaps the simplest of all elements, because a DocBlock for a class makes full use of the object-oriented principles that PHP offers and inherits the following information from the superclass (unless overridden):

• Summary
• Description
• The following tags:
  • author
  • copyright
  • package
  • subpackage
  • version

As hinted at in the opening text of this chapter each of the above will only be inherited if the child’s DocBlock does not have the inherited element. So, for example, if the DocBlock of a subclass has a summary then it will not receive the superclass’ summary.

The @subpackage tag will only be inherited if the parent’s @package matches the @package tag of the subclass; otherwise subpackages would ‘bleed’ through into other packages where they are not desired.

Properties

Inheritance for properties functions similar to classes and interfaces. When a superclass of the current class contains a property with the same name (hence, this property is re-defined) then the following information is inherited from that overridden property:

• Summary
• Description
• The following tags:
  • author
  • copyright
  • version
  • var

As with classes, each of the above will only be inherited if the redefined property’s DocBlock does not have the element that is to be inherited. So, for example, if the DocBlock of the redefined property has a summary then it will not receive the overridden property’s summary.

Methods

Inheritance for methods functions similar to classes and interfaces. When a superclass of the current class contains a method with the same name (hence, this method is re-defined) then the following information is inherited from that overridden method:

• Summary
• Description
• The following tags:
  • author
  • copyright
  • version
  • param
  • return
  • throws

As with classes, each of the above will only be inherited if the redefined method’s DocBlock does not have the element that is to be inherited. So, for example, if the DocBlock of the redefined method has a summary then it will not receive the overridden method’s summary.

Related topics

• Inheritance, for a complete, and more elaborate, reference on inheritance.
• ../references/phpdoc/tags/inline/inheritdoc, for a full description of the @inheritDoc inline tag.