README

XHP is a PHP extension which augments the syntax of the language such that XML document fragments become valid PHP expressions. This allows you to use PHP as a stricter templating engine and offers much more straightforward implementation of reusable components.

This repository contains the PHP class library, which is required to use XHP both under PHP7. The PHP7 extension is available at https://github.com/KMK-ONLINE/xhp-php7-extension

If you want a high-level XHP UI library, you might want to take a look at https://github.com/hhvm/xhp-bootstrap/

Installation

Composer is the recommended installation method. To add XHP to your project, add the following to your composer.json then re-run composer:

<code>
  "require": {
    "kmklabs/xhp": "1.6.*"
  }

Simple Example

<?php
$href = 'http://www.facebook.com';
echo <a href={$href}>Facebook</a>;

Take note of the syntax on line 3, this is not a string. This is the major new syntax that XHP introduces to PHP.

Anything that’s in {}’s is interpreted as a full PHP expression. This differs from {}’s in double-quoted strings; double-quoted strings can only contain variables.

You can define arbitrary elements that can be instantiated in PHP. Under the covers each element you create is an instance of a class. To define new elements you just define a new class. XHP comes with a set of predefined elements which implement most of HTML for you.

Complex Structures

Note that XHP structures can be arbitrarily complex. This is a valid XHP program:

<?php
$post =
  <div class="post">
    <h2>{$post}</h2>
    <p><span>Hey there.</span></p>
    <a href={$like_link}>Like</a>
  </div>;

One advantage that XHP has over string construction is that it enforces correct markup structure at compile time. That is, the expression $foo = <h1>Header</h2>; is not a valid expression, because you can not close an h1 tag with a /h2. When building large chunks of markup it can be difficult to be totally correct. With XHP the compiler now checks your work and will refuse to run until the markup is correct.

Dynamic Structures

Sometimes it may be useful to create a bunch of elements and dynamically add them as children to an element. All XHP objects support the appendChild method which behaves similarly to the same Javascript method. For example:

<?php
$list = <ul />;
foreach ($items as $item) {
  $list->appendChild(<li>{$item}</li>);
}

In the code, <ul /> creates a ul with no children. Then we dynamically append children to it for each item in the $items list.

Escaping

An interesting feature of XHP is the idea of automatic escaping. In vanilla PHP if you want to render input from the user you must manually escape it. This practice is error-prone and has been proven over time to be an untenable solution. It increases cod