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Hello World!

The PHP-JS extension is centered around the JS\Context class. This class represents a completely isolated instance of the V8 Javascript engine - similar to for example the window object in a page of a webbrowser. Variables and functions declared in one context are not visible to any other context instance.

Creating a context

The JS\Context constructor does not take any parameters, and can thus be constructed like this:

<?php
// create a new Javascript context
$context = new JS\Context();
?>

Evaluating a piece of javascript code

After construction, the context can be used to evaluate javascripts, using the evaluate() method. This method returns the value of the last executed statement. The method takes exactly one parameter, a string, with the javascript code to execute.

<?php
// create a new context
$context = new JS\Context;

// execute a statement concatenating into a very well-known greeting
$result = $context->evaluate("'Hello world!'");

// result now contains the string "Hello world!"
var_dump($result);
?>

The return value

The return value of the evaluate() method is the value of the last evaluated expression in the Javascript. If the script contains multiple statements, the value of the last statement is returned.

<?php
// create a new context
$context = new JS\Context;

// execute a statement concatenating into a very well-known greeting
$result = $context->evaluate("var x = 3; var y = 4; var z = x + y; ++z;");

// result now contains the integer 8
var_dump($result);
?>

Assigning data

Things start to become interesting once you start assigning PHP variables to the Javascript engine. The javascript code can use data from PHP context:

<?php
// create a new context
$context = new JS\Context;

// assign data to the javascript engine
$context->assign('language', 'dutch');
$context->assign('name', 'Emiel');

// execute a statement concatenating into a very well-known greeting
$result = $context->evaluate("var x = language == 'dutch' ? ('Hallo ' + name) : ('Hello ' + name);");

// result now contains the string "Hallo Emiel" (because the language was set to dutch)
var_dump($result);
?>