My previous example in part 2 was just “hello world”, so I’m going to try for something more like the real world. You may find this example unusual, but it does work. I took the PageRange class I used in my July 2007 php|architect article and converted it to the JavaScript style. The class is a variation on Martin Fowler’s Range pattern, and is the hub of a re-implementation of the main functionality of PEAR Pager, using a more object-oriented style.

A Range object is defined by just two values (three in my variation), so it might seem like too much to have an object just to keep these values, but as you can see from the example, a Range class can have behaviors to change and compare ranges.

As before, I’m defining most of the methods inside the constructor.

<?php
class PageRange {
    public $start;
    public $end;
    public $length;

    private $moveToStartAt;
    private $moveToEndAt;
    private $changeLengthToEndAt;
    private $includes;
    private $isInside;
    private $extendsBeyondStartOf;
    private $extendsBeyondEndOf;
    private $truncateToFitInside;
    private $moveToFitInside;
    private $asArray;

    public function __construct($start,$end,$length) {
        $self = $this;
        $this->start = $start;
        $this->end = $end;
        $this->length = $length;

        $this->moveToStartAt = function($start) use ($self) {
            return PageRange::withStartAndLength(
                $start,$self->length);
        };

        $this->moveToEndAt = function($end) use ($self) {
            return PageRange::withEndAndLength($end,$self->length);
        };

        $this->changeLengthToEndAt = function($end) use ($self) {
            return PageRange::withStartAndEnd($self->start,$end);
        };

        // Comparisons

        $this->includes = function($page) use ($self) {
            return $page >= $self->start
                && $page <= $self->end;
        };

        $this->isInside = function($range) use ($self) {
            return $range->includes($self->getStart())
                && $range->includes($self->getEnd());
        };

        $this->extendsBeyondStartOf = function(PageRange $range) use ($self) {
            return ($self->getStart() < $range->getStart());
        };

        $this->extendsBeyondEndOf = function(PageRange $range) use ($self) {
            return ($self->getEnd() > $range->getEnd());
        };

        // Changes

        $this->truncateToFitInside = function(PageRange $larger) use ($self) {
            if ($self->isInside($larger)) return clone $self;
            return $self->changeLengthToEndAt(
                $larger->getEnd());
        };

        $this->moveToFitInside = function(PageRange $larger) use ($self) {
            if ($self->isInside($larger)) return clone $self;
            if ($self->extendsBeyondEndOf($larger))
                return $self->moveToEndAt($larger->getEnd());
            if ($self->extendsBeyondStartOf($larger))
                return $self->moveToStartAt(
                    $larger->getStart());
        };

        // Convert to array

        $this->asArray = function() use ($self) {
            return range($self->start,$self->end);
        };

    }

I’ve defined the static methods in the usual way, non-JavaScript style. And there is, of course, the mandatory __call() method.

class PageRange...

    public function __call($method,$args) {
        return call_user_func_array($this->$method,$args);
    }

    public function getStart() { return $this->start; }

    public function getEnd() { return $this->end; }

    public function getLength() { return $this->length; }

    private static function calculateEnd($start,$length) {
        return $start + $length - 1;
    }

    private static function calculateStart($end,$length) {
        return $end - $length + 1;
    }

    private static function calculateLength($start,$end) {
        return $end - $start + 1;
    }

    public static function withStartAndLength(
        $start,$length)
    {
        return new self(
            $start,
            self::calculateEnd($start,$length),
            $length
        );
    }

    public static function withEndAndLength($end,$length) {
        return new self(
            self::calculateStart($end,$length),
            $end,
            $length
        );
    }

    public static function withStartAndEnd($start,$end) {
        return new self(
            $start,
            $end,
            self::calculateLength($start,$end)
        );
    }

}

An interesting aspect of this class is the fact that the constructor is private, so you have to use one of the creation methods. That’s part of my variation on the range pattern.

After the previous post in this series, additional independent implementations of the idea of JavaScript-style classes have turned up. So I’m going to list them and comment briefly on the differences. I hope this will be helpful to anyone who actually wants to use this in practice and needs to decide on the details of the implementation. Here are the links in chronological order:

• Ionut G. Stan:Javascript style PHP with PHP 5.3.0 (forum posting).
• Fredrik Holmström: Javascript-OO & Python-DuckTyping in PHP5.3.
• John Mertic: What’s new in PHP V5.3, Part 2: Closures and lambda functions.
• My own previous article.
• Andrea Giammarchi: A JavaScript Object Like PHP Class.

One difference is how JavaScript-like the implementations are. Some of them implement a syntax that is deliberately made to resemble JavaScript. Andrea Giammarchi’s version even uses ArrayAccess to make it possible to access object properties using both object and array syntax, as in JavaScript. At the other extreme is my implementation. I’ve tried to make it as similar to a regular PHP class as possible. You can instantiate an object in the same way as with an ordinary PHP class. This comes from defining the methods inside the class constructor.

After seeing all of these, I prefer my own way of doing it, except that it lacks what I mentioned in the previous article: an exception when you try to call an unrecognized method. But I’m obviously not objective, and I may have have missed something.