Contao\Model\Registry::register PHP Method

    public function register(Model $objModel)
    {
        $intObjectId = spl_object_hash($objModel);
        // The model has been registered already
        if (isset($this->arrIdentities[$intObjectId])) {
            return;
        }
        $strTable = $objModel->getTable();
        if (!is_array($this->arrAliases[$strTable])) {
            $this->arrAliases[$strTable] = array();
        }
        if (!is_array($this->arrRegistry[$strTable])) {
            $this->arrRegistry[$strTable] = array();
        }
        $strPk = $objModel->getPk();
        $varPk = $objModel->{$strPk};
        // Another model object is pointing to the DB record already
        if (isset($this->arrRegistry[$strTable][$varPk])) {
            throw new \RuntimeException("The registry already contains an instance for {$strTable}::{$strPk}({$varPk})");
        }
        $this->arrIdentities[$intObjectId] = $objModel;
        $this->arrRegistry[$strTable][$varPk] = $objModel;
        // Allow the model to modify the registry
        $objModel->onRegister($this);
    }