src/Forms/TreeDropdownField.php
public function setFilterFunction($callback)
    {
        if (!is_callable($callback, true)) {
            throw new InvalidArgumentException('TreeDropdownField->setFilterCallback(): not passed a valid callback');
        }

        $this->filterCallback = $callback;
        return $this;
    }
public function setFilterFunction($callback)
    {
        if (!is_callable($callback, true)) {
            throw new InvalidArgumentException('TreeDropdownField->setFilterCallback(): not passed a valid callback');
        }

        $this->filterCallback = $callback;
        return $this;
    }
public function setFilterFunction ( $ callback ) { if ( ! is_callable ( $ callback , true ) ) { throw new InvalidArgumentException ( 'TreeDropdownField->setFilterCallback(): not passed a valid callback' ) ; } $ this -> filterCallback = $ callback ; return $ this ; }
Set a callback used to filter the values of the tree before
displaying to the user.

@param callable $callback
@return $this
Set a callback used to filter the values of the tree before displaying to the user .