map object properties to parameters in a database query. Result Maps
finish the job by mapping the result of a database query (a set of columns) to
object properties. Next to Mapped Statements, the Result Map is probably one
of the most commonly used and most important features to understand.
A Result Map lets you control how data is extracted from the result of a
query, and how the columns are mapped to object properties. A Result Map can
describe the column type, a null value replacement, and complex property
mappings including Collections. The following example shows the structure
of a <resultMap> element.
<result ... .../>
<result ... .../>
In the above example, the [brackets] indicate optional attributes.
The id attribute is required and provides a name for the statement to
reference. The class attribute is also required, and specifies the full
name of a PHP class. This is the class that will be instantiated and populated
based on the result mappings it contains.
The resultMap can contain any number of property mappings that map object
properties to the columns of a result element. The property mappings are
applied, and the columns are read, in the order that they are defined.
Maintaining the element order ensures consistent results between different
drivers and providers.
As with parameter classes, the result class must be a PHP class object or
The optional extends attribute can be set to the name of another
resultMap upon which to base this resultMap. All properties of the
"parent" resultMap will be included as part of this resultMap, and
values from the "parent" resultMap are set before any values specified
by this resultMap. The effect is similar to extending a class.
The "parent" resultMap must be defined in the file before the extending
resultMap. The classes for the parent and child resultMaps need not be
the same, and do not need to be related in any way.