public function defineOperator(string $operator, callable $transformer): void
    {
        unset($this->inlineOperators[$operator]);
        $this->operators[$operator] = $transformer;
    }
public function defineOperator(string $operator, callable $transformer): void
    {
        unset($this->inlineOperators[$operator]);
        $this->operators[$operator] = $transformer;
    }
public function defineOperator ( string $ operator , callable $ transformer ) : void { unset ( $ this -> inlineOperators [ $ operator ] ) ; $ this -> operators [ $ operator ] = $ transformer ; }
Define an operator.

@param string   $operator    The operator's name.
@param callable $transformer Callable.
Define an operator .