public function __construct($operator, $field, $value, $dqlAlias = null)
{
if (!in_array($operator, self::$operators)) {
throw new InvalidArgumentException(sprintf('"%s" is not a valid comparison operator. Valid operators are: "%s"', $operator, implode(', ', self::$operators)));
}
$this->operator = $operator;
$this->field = $field;
$this->value = $value;
$this->dqlAlias = $dqlAlias;
}