My own PHP native template engine in ~90 lines of code!

PTpl.php

<?php

/*

----------------------------------------------
TEMPLATE EXAMPLES:
----------------------------------------------

----------------------------------------
htmlpage_base2.ptpl
----------------------------------------

BASE2

<? $block('main_content') ?>
  BASE2 main_content BLOCK
<? $endblock() ?>

----------------------------------------
htmlpage_base.ptpl
----------------------------------------

<? $extends('htmlpage_base2.ptpl') ?>

<nav>
  NAV HEAD
</nav>

<? $block('main_content') ?>
  DEFAULT <?=$model['a']?> TEST
<? $endblock() ?>

<hr>
FOOTER

----------------------------------------
index.ptpl
----------------------------------------

<? $extends('htmlpage_base.ptpl') ?>

BASE1 HEAD

<? $block('main_content') ?>
<? $block(null,['spaceless']) ?>
  PRE

   <main>
    INCLUDE WITH DIFFERENT MODEL:
    <?=$include('htmlpage_base.ptpl',['a'=>'NX'])?>
   </main>

   <? $block('main_content3') ?>
      <span>
      B1
      </span>

      <span>
      B2
      </span>
   <? $endblock() ?>

   POST
<? $endblock() ?>
<? $endblock() ?>

<?=$model['a']?>

BASE1 FOOTER

----------------------------------------
email_notify.ptpl
----------------------------------------

<? $block('subject') ?>
  Subject with model data <?=$model[user][name]?> <?=$model[user][surname]?>!
<? $endblock() ?>

<? $block('body_html') ?>
  MESSAGE BODY HTML
  <?=print_r($model,true)?>
<? $endblock() ?>

<? $block('body_text') ?>
  MESSAGE BODY TEXT
<? $endblock() ?>


----------------------------------------------
USAGE:
----------------------------------------------

$ptpl = new \PTpl("/template/base_path",array(
  'global_variable1' => 'global_value1',
  'global_variable2' => 'global_value2',
));

$tpl_globals = array('model'=>array(
  'model_value1' => 'value1',
  'model_value2' => 'value2',
));

$tpl_output_string = $ptpl->render("index.ptpl",$tpl_globals);
$tpl_data = $ptpl->render("index.ptpl",$tpl_globals,true);

----------------------------------------------
OUTPUT FILTERS:
----------------------------------------------

THERE IS A ALSO AN OUTPUT FILTER MECHANISM:
by default the block output is trimmed and an additional 'spaceless' filter is available
you can pass an array of filter names to the second argument of $block()
also note that the $block() first argument (the block name) is optional for example you can do:
<? $block(null,['spaceless']) ?>
for filter definitions and apply global filters see:
$ptpl->output_filters_def
and
$ptpl->->global_output_filters

*/


class PTpl {
  public $bp = null;
  public $global_extract_model;
  public $output_filters_def;
  public $global_output_filters;
  function __construct($bp,$global_extract_model=null) {
    $this->bp = $bp;
    $this->global_extract_model = $global_extract_model?:array();
    $this->output_filters_def = array(
      'trim' => 'trim',
      'spaceless' => array($this,'spacelessOutputFilter')
    );
    $this->global_output_filters = array(
      'trim',
    );
  }
  public function spacelessOutputFilter($input,$block_info) {
    return preg_replace('#>\s+<#','><',$input);
  }
  function render($path,$extract_model=array()) {
    $extract_model = array_merge($this->global_extract_model,$extract_model);
    extract($extract_model);

    $self = $this;
    $str_from = array('\\','/');
    $str_to = array(DIRECTORY_SEPARATOR,DIRECTORY_SEPARATOR);
    $tpl_basepath = $this->bp;
    $tpl_basepath = trim($tpl_basepath,'\\/');
    $tpl_extends = null;
    $block_stack = array();
    $blocks = array();

    $extends = function($tpl_path) use(&$tpl_extends) {
      $tpl_extends = $tpl_path;
    };
    $block = function() use(&$block_stack) {
      $block_args = func_get_args();
      array_push($block_stack,$block_args);
      ob_start();
    };
    $endblock = function() use(&$blocks,&$block_stack,$self) {
      $block_output = ob_get_clean();
      $block_args = array_pop($block_stack);
      $block_name = $block_args[0];
      $output_filters = $block_args[1];
      $output_filters = array_merge($self->global_output_filters?:array(),
                                    $output_filters?:array());
      foreach ($output_filters as $of_name) {
        $of_callable = $self->output_filters_def[$of_name];
        if(!$of_callable)
          continue;
        $block_output = call_user_func_array($of_callable,array($block_output,$block_args));
      }
      if(!$block_name) {
        echo $block_output;
        return;
      } else {
        if(!array_key_exists($block_name,$blocks) || $block_name=='_output')
          $blocks[$block_name] = $block_output;
        echo $blocks[$block_name];
      }
    };
    $include = function($tpl_path,&$inc_model=null) use($self,&$extract_model) {
      $tpl_data = $self->render($tpl_path,$inc_model?:$extract_model);
      return $tpl_data['_output'];
    };

    $prev_level = ob_get_level();
    ob_start();
    try {
      $curr_tpl = $path;
      while($curr_tpl) {
        $tpl_extends = null;
        $tpl_full_path = $tpl_basepath.DIRECTORY_SEPARATOR.$curr_tpl;
        $tpl_full_path = str_replace($str_from,$str_to,$tpl_full_path);
        $block('_output');
        include $tpl_full_path;
        $endblock('_output');
        $curr_tpl = $tpl_extends?:null;
      }
    } catch(\Exception $ex) {
      $blocks['_error'] = $ex;
    }
    while(ob_get_level()!=$prev_level) {
      ob_end_clean();
    }

    return $blocks;
  }
}