frontTemplate.php

<?php

class MegaOffice {

	public $page;
	protected $dirParts = './parts/';
	protected $dirPages = './pages/';

	function __construct(){
		$this->page = ($_GET['page'])? $_GET['page'] : 'index';
	}

	protected function replaceParts($content){

		$parts = array();
		preg_match_all("/\{\{(.+?)\}\}/is", $content, $layoutParts);
		if(count($layoutParts)){
			$parts = $layoutParts[1];
		}

		if(count($parts)){
			foreach ($parts as $num => $part) {
				
				$partHTML = $this->getTemplateFile($this->dirParts, $part);
				
				if($partHTML){
					$partHTML = $this->replaceParts($partHTML);
				}

				if(!$partHTML && $partHTML !== ''){
					$partHTML = '<h1 style="color:red;position:relative;display:block;">шаблон ' . $part . ' не найден </h1>';
				}
				$content = str_replace($layoutParts[0][$num], $partHTML, $content);
			}
		}

		return $content;

	}
	protected function getTemplateFile($dir, $name){
		$file = $dir . $name . '.htm';
		return @file_get_contents($file);
	}
	protected function getPageTemplate($name){
		return $this->getTemplateFile($this->dirPages, $name);
	}


	public function render(){
		$content = $this->getPageTemplate($this->page);

		if(!$content){
			return  'Страница не найдена <a href="/new/html/">go to index </a>';
		}

		return $this->replaceParts($content);
	}

}

$Office = new MegaOffice();
echo $Office->render();