h2o code generation concept, 4 and 5 are executable code

1. template.html

<h1>{{ person.name }}</h1>
{% block content %}
    <small>block:{{ block.name }}, level: {{ block.depth }} ?></small>
    (i am {{ block.age }} years old)
{% endblock %}
<ul>
{% for hobby in person.hobbies %}
  <li>{{ hobby|capitalize }}</li>
{% endfor %}
</ul>

2. child_template.html

{% extends 'template.html' %}
{% block content %}
    <small>block:{{ block.name }}, level: {{ block.depth }} ?></small>
    (says hello from sub template)
    {{ block.super }}
{% endblock %}

3. child_child_template.html

{% extends 'child_template.html' %}
{% block content %}
    <small>block:{{ block.name }}, level: {{ block.depth }} ?></small>
    (says hello from sub sub template)
    {{ block.super }}
{% endblock %}

4. child_child_template.compile.php

<?php
include 'lib.php';
$person = array('name'=>'taylor', 'age'=>18, 'hobbies'=>array('watch tv','swimming'));
$c = new Context(compact('person'));
?>

<h1><?= $c['person.name'] ?></h1>

<? // Content block
function block_content_1($c) {?>
    <small>block: <?= $c['block.name']?>, level: <?= $c['block.depth'] ?></small>
    (i am <?= $c['person.age'] ?> years old)
<?}
function block_content_2($c) {?>
    <small>block: <?= $c['block.name']?>, level: <?= $c['block.depth'] ?></small>
    (says hello from sub template)
    <?= $c['block.super'] ?>
<?}
function block_content_3($c) {?>
    <small>block: <?= $c['block.name']?>, level: <?= $c['block.depth'] ?></small>
    (says hello from sub sub template)
    <?= $c['block.super'] ?>
<?}
?>
<?= Block::register('content', 3, $c) ?>

<h3>i'd like to</h3>
<ul>
<? foreach((array)$c['person.hobbies'] as $hobby): 
$c->push(compact('hobby'));
?>
    <li><?= ucwords($c['hobby']) ?></li>

<? 
$c->pop();
endforeach ?>
</li>

lib.php

<?php
class Context extends ArrayObject {
    function __construct($scope = array()) {
        $this->scopes = array($scope);
    }

    function resolve($path) {
        $parts = explode('.', $path);
        $target = $this[array_shift($parts)];

        foreach($parts as $part) {
            if (is_array($target) && isset($target[$part]))
                $target = $target[$part];
            elseif (is_object($target) && property_exists($target, $part))
                $target = $target->$part;
            elseif (is_object($target) && method_exists($target, $part))
                $target = $target->$part();
            else return null;
        }
        return $target;
    }
    
    function pop() {
        array_shift($this->scopes);
    }
    
    function push($stack = array()) {
        array_unshift($this->scopes, $stack);
    }

    function offsetGet($key) {
        if (strpos($key, '.') !== false)
            return $this->resolve($key);
        
        foreach ($this->scopes as &$layer) {
            if (isset($layer[$key]))
                return $layer[$key];
        }
    }
    
    function offsetExists($key) {
        return $this->offsetGet($key) !== null;
    }
    
    function offsetSet($key, $value) {
        $this->scopes[0][$key] = $value;
    }
    
}

class Block {
    var $name, $depth, $super;
    var $context;
    
    function __construct($name, $depth, $context) {
        $this->depth = $depth;
        $this->name = $name;
        $this->context = $context;
    }
    
    function __toString() {
        $callback = "block_{$this->name}_{$this->depth}";
        $this->context->push(array('block'=>$this));
        $callback($this->context);
        $this->context->pop();
        return '';
    }

    static function register($name, $depth, $c) {
        $blocks = array();
        for ($i=0; $i < $depth; $i++) {
            $blocks[$i] = $block =& new Block($name, $i+1, $c);
            if ($i) {
                $block->super =& $blocks[$i-1];
            }
        }
        return end($blocks);
    }
}
?>