h1. Archived Repo

This project is a fork from Facebook's archive repo at https://github.com/facebookarchive/xhp-php5-extension

PHP7 support is provided as a community project and not by Facebook, nor is this fork endorsed by the company.

This project just contains the PHP extension and core tests. The class library (which is required for this extension to be useful) is available at https://github.com/phplang/xhp-lib .

HHVM users get XHP support by default in HackLang files, and should use the official HackLang XHP library at https://github.com/facebook/xhp-lib

h1. Introduction

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.

h1. Simple Example

bc. <?php $href = 'http://www.facebook.com'; echo Facebook;

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.

Important: Please be sure to include "init.php":http://github.com/facebook/xhp/blob/master/php-lib/init.php which is in the "php-lib":http://github.com/facebook/xhp/tree/master/php-lib/ directory of the repository. The XHP extension only handles adding the XML syntax, the actual elements are defined directly in PHP. Including the core XHP libraries in PHP code means you can customize XHP for your own applications, though it's recommended to avoid large forks which may cause incompatibilities as XHP evolves. All the examples you see on this page omit the required includes.

h1. Complex Structures

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

bc. <?php $post =

; One advantage that XHP has over string construction is that it enforces correct markup structure at compile time. That is, the expression @$foo =

Header

;@ 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. h1. 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: bc. ; foreach ($items as $item) { $list->appendChild(

{$item}

); } In the code, @

@ creates a ul with no children. Then we dynamically append children to it for each item in the @$items@ list. h1. Escaping An interesting feature of XHP is the idea of automatic escaping. In vanilla PHP if you want to render input from the user you must manually escape it. This practice is error-prone and has been proven over time to be an untenable solution. It increases code complexity and still leads to security vulnerabilities by careless programming. However, since XHP has context-specific about the page structure it can automatically escape data. The following two examples are identical, and both are "safe". bc. Hello '.htmlspecialchars($_GET['name']).'