Building a simple template engine in PHP.

Yes that’s another template engine in PHP. I’ve been using Smarty for years. It’s easy to install and easy to use. But there is something I don’t like in Smarty. I need to learn another language (smarty markup) to create my templates. Normally my templates are not very complex. I only use them to move HTML code outside PHP. Basically my templates are: HTML and some variables that pass from PHP to tpl. Sometimes I need to do a loop. I know Smarty has a lot of helpers but I never use them.

Now I’m in a project and I must to choose a template engine. This project don’t have any dependencies to any other libraries, so I don’t want to include full Smarty library to my simple templates. A quick search in Google gives us a list of template engines in PHP. Mostly all engines use PHP as template language. That’s a good decision. In fact PHP is a template language so, why we need to use another one?. I think the main problem of using PHP as template language is the temptation of put logic in the template and have a nice spaghetti code.

So I am going to build a simple template engine. Let’s start:
As always I like to start from the interface. When I start a library I like to think the library is finished (before start coding. cool isn’t it?) and write the code to use it. Finally when the I like the interface I start coding the library.

I want this template:

<h1>Example of tpl</h1>
var1 = _('var1') ?>
var2 = _('var2') ?>
foreach ($this->_('var3') as $item) {
    echo $this->clean($item);

And I want to call it with something like this:

echo Tpl::singleton()->init('demo1.phtml')->render(array(
    'var1' => 1,
    'var2' => 2,
    'var3' => array(1, 2, 3, 4, 5, 6, 7)

Basically Tpl class will be a container to collect the configuration and init function will be a factory of another class (Tpl_Instance) that will do the templating itself.

render function is the main function. Basically call to php’s include function with the selected tpl.

if (!is_file($_tplFile)) {
    throw new Exception('Template file not found');

include ($_tplFile);

$out = ob_get_contents();

return $out;

As we see the tpl file is a simple PHP file included in our script with Tpl_Instance::render. So $this in our tpl’s PHP code is the instance of Tpl_Instance. That means whe can use protected and even private functions of Tpl_Instance.

Now I going to show different usages of the library:

// Sets the path of templates. If nuls asumes file is absolute
Tpl::singleton()->setConf(Tpl::TPL_DIR, realpath(dirname(__FILE__)));
echo Tpl::singleton()->init('demo1.phtml')->render(array(
    'var1' => 1,
    'var2' => 2,
    'var3' => array(1, 2, 3, 4, 5, 6, 7)
// The same instance a different template and params added in a different way
$tpl = Tpl::singleton()->init('demo2.phtml');
$tpl->addParam('header', 'header');
$tpl->addParam('footer', 'footer');
echo $tpl->render();
// Disable exceptions if we don't assign a variable
Tpl::singleton()->setConf(Tpl::THROW_EXCEPTION_WITH_PARAMS, false);
$tpl = Tpl::singleton()->init('demo1.phtml');
$tpl->addParam('var1', 'aaaa');
$tpl->addParam('var3', array(1, 2, 3, 4, 5, 6, 7));
echo $tpl->render();
// Using factory
$objTpl = Tpl::factory();
$objTpl->setConf(Tpl::THROW_EXCEPTION_WITH_PARAMS, true);
try {
    $tpl = $objTpl->init('demo1.phtml');
    $tpl->addParam('var1', 'aaaa');
    $tpl->addParam('var3', array(1, 2, 3, 4, 5, 6, 7));
    echo $tpl->render();
} catch (Exception $e) {
    echo "" . $e->getMessage() . "


And like always full source code is available on google code.

About Gonzalo Ayuso

Web Architect. PHP, Python, Node, Angular, ionic, PostgreSQL, Linux, ... Always learning.

Posted on February 21, 2010, in php, Technology, Web Development. Bookmark the permalink. 2 Comments.

  1. I think if temptation of putting logic in the template is the only motivator to use a template engine. Your template engine is not going to prevent it because the template is a php file.

    I think your template engine can be reduced to one function

    function render((string) $template,(array) $vars)

    return ob_get_clean();

    If you want to create a minimal template engine don’t add fat.

    • Totally agree. The temptation of building logic in the template is the bad side of using php as template language. But I preffer this risk than building a new language.
      In the other side, basically the template engine is almost like you say. I use two classes because I want to use the interface I show you in the examples. I know I can reduce the code to the example you show and I can reduce the library to one class instead of two but the main objetive for me if the interface

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