* where 'varName' refers to the name of the variable/property that the related object(s) can
* be accessed through; 'relationType' refers to the type of the relation, which can be one of the
* following four constants: self::BELONGS_TO, self::HAS_ONE, self::HAS_MANY and self::MANY_MANY;
* 'className' refers to the name of the active record class that the related object(s) is of;
* and 'foreign_key' states the foreign key that relates the two kinds of active record.
* Note, for composite foreign keys, they must be listed together, separated by commas;
* and for foreign keys used in MANY_MANY relation, the joining table must be declared as well
* (e.g. 'join_table(fk1, fk2)').
*
* Additional options may be specified as name-value pairs in the rest array elements:
* <ul>
* <li>'select': string|array, a list of columns to be selected. Defaults to '*', meaning all columns.
* Column names should be disambiguated if they appear in an expression (e.g. COUNT(relationName.name) AS name_count).</li>
* <li>'condition': string, the WHERE clause. Defaults to empty. Note, column references need to
* be disambiguated with prefix 'relationName.' (e.g. relationName.age>20)</li>
* <li>'order': string, the ORDER BY clause. Defaults to empty. Note, column references need to
* be disambiguated with prefix 'relationName.' (e.g. relationName.age DESC)</li>
* <li>'with': string|array, a list of child related objects that should be loaded together with this object.
* Note, this is only honored by lazy loading, not eager loading.</li>
* <li>'joinType': type of join. Defaults to 'LEFT OUTER JOIN'.</li>
* <li>'alias': the alias for the table associated with this relationship.
* This option has been available since version 1.0.1. It defaults to null,
* meaning the table alias is the same as the relation name.</li>
* <li>'params': the parameters to be bound to the generated SQL statement.
* This should be given as an array of name-value pairs. This option has been
* available since version 1.0.3.</li>
* <li>'on': the ON clause. The condition specified here will be appended
* to the joining condition using the AND operator. This option has been
* available since version 1.0.2.</li>
* <li>'index': the name of the column whose values should be used as keys
* of the array that stores related objects. This option is only available to
* HAS_MANY and MANY_MANY relations. This option has been available since version 1.0.7.</li>
* <li>'scopes': scopes to apply. In case of a single scope can be used like 'scopes'=>'scopeName',
* in case of multiple scopes can be used like 'scopes'=>array('scopeName1','scopeName2').
* This option has been available since version 1.1.9.</li>
* </ul>
*
* The following options are available for certain relations when lazy loading:
* <ul>
* <li>'group': string, the GROUP BY clause. Defaults to empty. Note, column references need to
* be disambiguated with prefix 'relationName.' (e.g. relationName.age). This option only applies to HAS_MANY and MANY_MANY relations.</li>
* <li>'having': string, the HAVING clause. Defaults to empty. Note, column references need to
* be disambiguated with prefix 'relationName.' (e.g. relationName.age). This option only applies to HAS_MANY and MANY_MANY relations.</li>
* <li>'limit': limit of the rows to be selected. This option does not apply to BELONGS_TO relation.</li>
* <li>'offset': offset of the rows to be selected. This option does not apply to BELONGS_TO relation.</li>
* <li>'through': name of the model's relation that will be used as a bridge when getting related data. Can be set only for HAS_ONE and HAS_MANY. This option has been available since version 1.1.7.</li>
* </ul>
*
* Below is an example declaring related objects for 'Post' active record class: