Bringing Javascript to the server using PHP * update *

Christophe Robin — Thu, 19 Feb 2009 14:38:09 +0000

I’ve been working for the last month on my first PHP extension since 2 years ago, a nice way to learn the new stuff Zend had in store for PHP 5.3. This extension is named SpiderMonkey, and embed the original engine made by Mozilla and available on most Linux distributions.

SpiderMonkey

SpiderMonkey is the Javascript engine used by Mozilla’s main products. It provide a nice C API for executing and interacting with Javascript. I base myself on the 1.7.0 version, which is the latest stable version. 1.8.0 is supposed to come soon but is still under development.

Usage

The API is straight-forward, a Javascript Runtime is first created, it’s a container for all “global” variables and Javascript Contexts. Contexts is the global scope where your program runs, all scripts executed on the same contexts will share the same global variables.

This part changed in rev. 38, see below

/* Initialisation of extension */
$rt = new JSRuntime();
/* Create a single context, most application will only use
* one context while a server ( like the pinetd httpd server )
* would create a context by request */
$ctx = $rt->createContext();

Since rev. 38, you don’t need to instanciate the JSRuntime anymore

/* Create a single context, most application will only use
* one context while a server ( like the pinetd httpd server )
* would create a context by request */
$ctx = new JSContext();

Once the context created, you’ll want to do two things:

Assign values from PHP to JS
Register functions from PHP to JS

For now, variables assigned from PHP are converted to a new Javascript variable and changing them in JS will not affect the original PHP value, while it’s supposed to be allowed later ( using a different function that will assign the variable as a reference and not a copy ), it’s already enough to provide $_GET, $_POST, $_FILES and the likes to JS. The only case where this change is for objects and resources, which keeps pointers to themselves thus allowing you to export a $dom variable containing a DOMDocument and acting on it by the mean of the object methods ( the object properties are not available ).

Exported functions are declared in the global scope.

Here is an exemple with mysqli:

/* Create a new database object */
$mysqli = new mysqli("host", "user", "pass", "db");
/* Allow Javascript to call sprintf under the name sprintf */
$ctx->registerFunction('sprintf', 'sprintf');
/* Provide our db connexion to Javascript */
$ctx->assign('db', $mysqli);

Then in Javascript you’d do:

/* i know the sprintf is not the best way to do it, but for readability
* i'll stick with it in this sample */
res = db.query(sprintf('SELECT * FROM my_table WHERE field = %s', db.escape_string(dynamic_data)))
if (res) {
while (line = res.fetch_assoc())
{
printf("%s\n", line.field2);
}
}

Because this is based on PHP 5.3, you could also use closures in the assign function, allowing things like:

$ctx->registerFunction('foo', function() { echo "bar"; });

Allowing you to create a function foo() that echo “bar” when called.

Future

A lot of new features are already being implemented, here is a non-exhaustive list:

Allowing to pass all variables as reference, allowing the Javascript to modify the PHP value
Allow to register “classes” prototypes, like:
$ctx->registerClass('DOMDocument');

Then you could just do “var a = DOMDocument();” in Javascript to instanciate the object.
Autoregister a prototype on some types of resources. A Stream resource could then be assigned in JS, and you could call stream.write, stream.read, etc…

How-to test ?

The whole source code is available on a public read-only SVN: https://ookoo.org/svn/pecl-spidermonkey. Be careful, you need PHP 5.3.0 beta 1 to compile it ( it will not even compile on PHP 5.2 ). There may be some issues when dealing with many objects so don’t use it for production purpose.

svn co https://ookoo.org/svn/pecl-spidermonkey
cd pecl-spidermonkey
phpize
./configure
make
./test.sh

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Bringing Javascript to the server using PHP * update *