public function getDefinitionIndex($id) {
        $definition = $this->getDefinition($id);

        foreach ($this->definitions as $index => $item) {
            if ($item === $definition) {
                return $index;
            }
        }
    }
public function getDefinitionIndex($id) {
        $definition = $this->getDefinition($id);

        foreach ($this->definitions as $index => $item) {
            if ($item === $definition) {
                return $index;
            }
        }
    }
@param $id

@return int|null|string