I\'m using NetBeans for PHP.
When I edit a .js file, it gives me javascript code completion.
How can I get it to also give me jQuery
The basic rule is that your jQuery (or for that matter any js lib) should be found in the same project you need auto complete to work. So just place jquery-1.x.y.js somewhere in your project (that can be reached by NetBeans as it reaches your js file) and you should be good to go.
To test you can put the jQuery file in the same folder as your js file being edited.