mustache-like template engine

gistfile1.php

<?php 

class Template {

	function __construct($code, $escape = null) {
		$this->code = $code;
		$this->preparsed = null;
		$this->escape = $escape;
	}

	private function preparseIfNessesary() {
		if ($this->preparsed != null) return $this->preparsed;
		$stack = array(0);
		$code = $this->code;

		// remove white-space between tags
		// $code = preg_replace('/(}})\s+({{)/si', '\1 \2', $code);
		
		// prepare block-tags to include level/rank information
		$code = preg_replace_callback('/{{(#|\^|\/)(\w+)}}/si', function ($m) use (&$stack) {
			list(,$mod,$name) = $m;
			switch ($mod) {
			case '#': // OPEN
			case '^': // OPEN
				$level = count($stack);
				$id = $level.".".(++$stack[$level-1]);
				array_push($stack, 0);
				break;
			case '/': // CLOSE
				array_pop($stack);
				$level = count($stack);
				$id = $level.".".($stack[$level-1]);
				break;
			}
			return '['.$mod.$name.'#'.$id.']';
		}, $code);

		$this->preparsed = $code;
		return $this->preparsed;
	}

	private function parsePlaceholders($code, $params) {

		$escape = $this->escape;
		
		$RECURSIVE = function ($code, $params) use (&$RECURSIVE, &$escape) {

			// parse blocks
			$code = preg_replace_callback('/'
					.'\[(#|\^)(([\w_\-]+)#([\d\.]+))]'
					.'((?:[^[]|\[(?!\/\2])|(?R))+)'
					.'\[\/\2]'
					.'/si',
				function ($m) use (&$params, &$RECURSIVE) {
					list(,$mod,,$varname,$level,$body) = $m;
					switch ($mod) {
					case '#': // IF OR LOOP
						$value = $params->{$varname};
						if ($value === null || $value === false) {
							return "";
						}
						if (!is_string($value) && is_callable($value)) {
							$body = call_user_func($value, array());
							return $RECURSIVE($body, $params);
						}
						if (is_array($value) || $value instanceof \Traversable) {
							$result = array();
							foreach ($value as $item) {
								if (!is_object($item)) {
									$item = (object)array("item" => $item, "parent" => &$params);
								}
								elseif (!isset($item->parent)) {
									$item->parent = &$params;
								}
								$result[] = rtrim($RECURSIVE($body, $item));
							}
							return implode("\n", $result);
						}
						if (is_object($value)) {
							if (!isset($value->parent)) {
								$value->parent = &$params;
							}
							return $RECURSIVE($body, $value);
						}
						return $RECURSIVE($body, $params);
					
					case '^': // IF NOT
						$value = $params->{$varname};
						if ($value) {
							return "";
						}
						return $RECURSIVE($body, $params);
					}
				},
				$code);
			
			// parse vars
			$code = preg_replace_callback('/{{(\w+)(?:|\s+([^{}]*?))}}/si',
				function ($m) use (&$params, &$RECURSIVE, &$escape) {
					list(,$varname,$args) = $m;
					$value = $params->{$varname};
					if ($value === null) {
						return "";
					}
					if (!is_string($value) && is_callable($value)) {
						$args = (!empty($args)) ? json_decode("[$args]") : array();
						return call_user_func($value,
							$args,
							$escape ?: function($v){return $v;},
							function ($code, $optionalParams = null) use (&$params, &$RECURSIVE, &$escape) {
								$subtmpl = new Template($code, $escape);
								return $subtmpl->transform($optionalParams ?: $params);
							});
					}
					if ($escape !== null) {
						$value = call_user_func($escape, (string)$value);
					}
					return (string)$value;
				},
				$code);

			return $code;
		};

		return $RECURSIVE($code, $params);
	}

	function transform($params) {
		$output = $this->preparseIfNessesary();
		$output = $this->parsePlaceholders($output, $params);
		return $output;
	}
}

if ($argv && realpath($argv[0]) == __FILE__) {

	$code = <<<CODE
<h1>{{header}}</h1>
{{#bug}}
{{/bug}}

<ul>
{{#items}}
  {{#first}}
    <li><strong>{{name}}</strong></li>
  {{/first}}
  {{#link}}
    <li><a href="{{url}}">{{name}}</a> lönk</li>
  {{/link}}
{{/items}}
</ul>

{{#empty}}
  <p>The list is empty.</p>
{{/empty}}
CODE;
	$json = <<<JSON
{
  "header": "Colors",
  "items": [
      {"name": "red", "first": true, "url": "#Red"},
      {"name": "green", "link": true, "url": "#Green"},
      {"name": "blue & green", "link": true, "url": "#Blue"}
  ],
  "empty": false
}
JSON;

	$tmpl = new Template($code, "htmlspecialchars");
	echo $tmpl->transform(json_decode($json));

}