PHP115

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Main Page >> Web Application Development >> Workbook >> Template Engines

Please note that this is an advanced topic. Make sure that you have worked through all the previous sections of this workbook before proceeding.

Template engines

There are many PHP template engines out there, there are some of the most popular ones:

  • Twig - probably the best current, framework-independent template engine.
  • Mustache - also very popular, but very simple and so not suitable for more complex projects.
  • Smarty - very old, and the website looks very dated, but the product itself is very good and still actively maintained!
  • Blade - Blade comes with Laravel, a very popular PHP framework, and cannot easily be used without Laravel.

In this tutorial we will look at Twig

Installing Twig

Please read the installation notes on the official website.

Simple example

First let's look at a simple example that passes variables to a template.

The template - index.html

<!DOCTYPE html>
<html>
    <head>
        <title>My first template</title>
    </head>
    <body>
        <h1>My Webpage</h1>
        
        {{ include('navigation.html') }}
        
        <p>{{ a_variable }}</p>
        <p>{{ another_variable|upper }}</p>
        
        <ul>
        {% for item in people %}
            <li>{{ item.FirstName }} {{ item.Surname }}</li>
        {% endfor %}        
        </ul>
        
    </body>
</html>

Things to note:

  • You can increase code reuse by including templates within template, in this case: include('navigation.html')
  • a_variable displays a simple variable.
  • another_variable|upper displays another variable, but converts it to uppercase. This is done using the "upper" extension.
  • for item in people allows you to loop through an array of items.

The navigation.html template, included in the file above, is fairly simple: 

<ul id="navigation">
  <li><a href="#">Page 1</a></li>
  <li><a href="#">Page 2</a></li>
  <li><a href="#">Page 3</a></li>
</ul>

The home file - index.php

<?php

// Point to library
require_once '../../vendor/autoload.php';

// Set up Environment
$loader = new \Twig\Loader\FilesystemLoader('.');
$twig = new \Twig\Environment($loader);

// Array of data
$people[0]['FirstName'] = "Alix";
$people[0]['Surname'] = "Bergeret";
$people[1]['FirstName'] = "Chris";
$people[1]['Surname'] = "Dennett";

// Load and render template
echo $twig->render('template.html', 
                   array('a_variable' => 'Alix', 
                         'another_variable' => 'Bergeret',
                         'people' => $people));

The result: https://mi-linux.wlv.ac.uk/~in9352/twig/workbook/

Let's look at the file above in more detail: 

require_once 'Twig/Autoloader.php';
Twig_Autoloader::register();

// Create loader object, pointing to templates folder
$loader = new Twig_Loader_Filesystem('templates');

// set-up environment without cache (for development) 
$twig = new Twig_Environment($loader);

The above essentially "sets up" Twig:

  • You specify where Twig is installed (via require_once). This might be different depending on where you have installed it, but please note that the folder containing Autoloader.php MUST be called "Twig" with a capital "T".
  • You specify where your templates folder is (in this case "templates")
  • You create a new environment to work with. Note: During development it is best NOT to use caching, as you would not see your changes when updating a templates. Only enable caching once the website is finished and deployed.
// Load and render template
echo $twig->render('index.html', 
                   array('a_variable' => 'Alix', 
                         'another_variable' => 'Bergeret',
                         'people' => $people));

The above renders the page. It takes 2 parameters:

  • The template you wish to use (in this case "index.html" - as defined above)
  • The data you wish to pass to the template, as an array. In this case 2 string values ("Alix" and "Bergeret") and an array called $people (defined just before the render command).

Database example

Let's revisit our pets database example, but this time we can separate logic from HTML.

The template - pets.html

The template itself is quite simple, and very similar to the "simple example" above. Note how we loop through an array of pets (the array is called "results"). 

<!DOCTYPE html>
<html>
    <head>
        <title>My pets</title>
    </head>
    <body>
        <h1>My pets webpage</h1>
        
        {{ include('navigation.html') }}
        
        <p>{{ num_rows }} record(s) were returned...</p>
        
        <table border=1>
        {% for item in results %}
          <tr>
            <td>{{ item.name }}</td>
            <td>{{ item.species }}</td>
          </tr>
        {% endfor %}        
        </table>        
        
    </body>
</html>

The main file - pets.php

<?php

// set-up environment without cache (for development) 
// Connect to server/database

// Run SQL query
$res = mysqli_query($mysqli, "SELECT name, species, age FROM pet");

// How many rows were returned?
$num_rows = mysqli_num_rows($res);

// Loop through resultset and put in array
while($row = mysqli_fetch_assoc($res)) {
  $results[] = $row;
}

// Load and render template
echo $twig->render('pets.html', 
                   array('num_rows' => $num_rows, 'results' => $results));


?>

Most of the above should be familiar by now. The only tricky part is: 

// Loop through resultset and put in array
while($row = mysqli_fetch_assoc($res)) {
  $results[] = $row;
}

We simply loop through the database resultset ($res), and insert each record in an array ($results). Then we can pass the array to the template on the next line: 

echo $twig->render('pets.html', 
                   array('num_rows' => $num_rows, 'results' => $results));

Result: http://mi-linux.wlv.ac.uk/~in9352/twig/pets.php

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