MANY_MANY relation support behavior for Yii framework

ManyManySupport.php

<?php
/**
 * This behavior is for a model having one or more MANY-MANY relations.
 *
 * You need a junction table:
 *
 * CREATE_TABLE self_target (
 *     self_id integer(11) NOT NULL,
 *     target_id integer(11) NOT NULL,
 *     ...
 * );
 *
 * and also definition like as:
 *
 * public function relations()
 * {
 *     return array(
 *         'target' => array(self::MANY_MANY, 'Target', 'self_target(self_id,target_id)', ...),
 *     );
 * }
 */
class ManyManySupport extends CActiveRecordBehavior
{
	/**
	 * @param string $relationName
	 * @throws CDbException
	 * @return CManyManyRelation
	 */
	protected function getManyManyRelation($relationName)
	{
		foreach ($this->owner->metaData->relations as $rel) {
			if ($rel->name == $relationName) {
				if ($rel instanceof CManyManyRelation) {
					return $rel;
				}
				else {
					throw new CDbException('The relation was not defined as Many-Many: ' . $relationName);
				}
			}
		}
		throw new CDbException('No such relation: ' . $relationName);
	}

	/**
	 * @param CActiveRecord $target
	 * @throws CDbException
	 * @return void
	 */
	protected function checkExistence($target) {
		if ($this->owner->isNewRecord) {
			throw new CDbException("Relation owner is not saved.");
		}
		if ($target->isNewRecord) {
			throw new CDbException("Relation target is not saved.");
		}
	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param CActiveRecord $target
	 * @return boolean
	 */
	public function isManyManyPeer($relationName, $target)
	{
		$this->checkExistence($target);
		return $this->isManyManyPeerByPk($relationName, $target->primaryKey);
	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param int $foreignPk
	 * @return boolean
	 */
	public function isManyManyPeerByPk($relationName, $foreignPk)
	{
		$cb = $this->owner->commandBuilder;
		$rel = $this->getManyManyRelation($relationName);
		return $cb->createCountCommand($rel->junctionTableName, $cb->createCriteria()->addColumnCondition(array(
			$rel->junctionForeignKeys[0]=>$this->owner->primaryKey,
			$rel->junctionForeignKeys[1]=>$foreignPk,
		)))->queryScalar() > 0 ? true : false;
	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param CActiveRecord $target
	 * @return void
	 * @throws CDbException
	 */
	public function bindManyMany($relationName, $target)
	{
		if ($this->isManyManyPeer($relationName, $target)) {
			return;
		}
		$this->__bindManyManyInternal($relationName, $target->primaryKey);

	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param int $foreignPk
	 * @return void
	 * @throws CDbException
	 */
	public function bindManyManyByPk($relationName, $foreignPk)
	{
		if ($this->isManyManyPeerByPk($relationName, $foreignPk)) {
			return;
		}
		$this->__bindManyManyInternal($relationName, $foreignPk);

	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param CActiveRecord $target
	 * @return void
	 * @throws CDbException
	 */
	public function unbindManyMany($relationName, $target)
	{
		if (!$this->isManyManyPeer($relationName, $target)) {
			return;
		}
		$this->__unbindManyManyInternal($relationName, $target->primaryKey);
	}

	/**
	 * Extended function
	 *
	 * @param string $relationName
	 * @param int $foreignPk
	 * @return void
	 * @throws CDbException
	 */
	public function unbindManyManyByPk($relationName, $foreignPk)
	{
		if (!$this->isManyManyPeerByPk($relationName, $foreignPk)) {
			return;
		}
		$this->__unbindManyManyInternal($relationName, $foreignPk);
	}

	/**
	 * @param $relationName
	 * @param $foreignPk
	 */
	protected function __bindManyManyInternal($relationName, $foreignPk)
	{
		// Already checked: $this->checkExistence($target);
		$cb = $this->owner->commandBuilder;
		$rel = $this->getManyManyRelation($relationName);
		$cb->createInsertCommand(
			$rel->junctionTableName,
			array(
				$rel->junctionForeignKeys[0] => $this->owner->id,
				$rel->junctionForeignKeys[1] => $foreignPk,
			)
		)->execute();
	}

	/**
	 * @param $relationName
	 * @param $foreignPk
	 */
	protected function __unbindManyManyInternal($relationName, $foreignPk)
	{
		// Already checked: $this->checkExistence($target);
		$cb = $this->owner->commandBuilder;
		$rel = $this->getManyManyRelation($relationName);
		$cb->createDeleteCommand(
			$rel->junctionTableName,
			$cb->createCriteria()->addColumnCondition(
				array(
					$rel->junctionForeignKeys[0] => $this->owner->id,
					$rel->junctionForeignKeys[1] => $foreignPk,
				)
			)
		)->execute();
	}
}