php - Check if my javascript is loaded on a site

Question

I have asked this question before but it seems i got misunderstood therefore i decided to ask again but this time with alot of information:

For the lazy reader my goal here is:

Is there a way to check if a javascript is enabled on an external site either from PHP or through Ajax

Detailed description:

Okay, so my company, has many clients, when these clients sign up on our website, they are handed a javascript. They can then use this script on their own website to get some extra features.

Now all of the websites, that a client has, is stored within our CMS system (like there is a list of all of the websites they have that are signed with us).

Now my boss gave me the following assignment:

We need a function so that the user can press the button "Test" and the system will test if the javascript is on their site and working without errors (i.e is there another script blocking ours).

Now the past couple of days, i have been trying to find similar cases on the web and the only thing i have been suggested, was Phantomjs however there are NO examples on how to even get close to what i want to achieve.

So my question to you:

1. is it possible to check if a site has a certain javascript.
2. is it possible to check if the javascript is running without errors(if the console throws errors or not)

I hope, that i wont get misunderstood this time :) if you have any questions, please just leave a message, and i will respond as fast as possible!

The phantomJs Solution (origianlly posted by Elias)

This is my code:

   var page = require('webpage').create();
page.onConsoleMessage = function( message, line, srcId)
{//show console errors for page
    console.log('Page has errors showing in console: ' + msg
        + ' (line: ' + (line || '?') + ', id: ' + srcId + ')');
};
page.open('http://www.marcrasmussen.com',function(status)
{
    if (status != 'success')
    {//can't load page
        console.log('Failed to open page: ' + status);
        phantom.exit();
        return;
    }
    var reslt = page.evaluate(function()
    {
        var usesOurScript = false,
            scripts = document.querySelectorAll('script');//get all script tags
        Array.forEach.apply(scripts, [function(elem)
        {//check all loaded scripts
              if (/jquery.js/.js.js.test(elem.getAttribute('src')))
            {//this src attribute refers your script
                usesOurScript = true;//set to true
            }
        }]);
        return {page: location.href, found: usesOurScript};//return its href and the use-status
    });
    //script was found? adjust message
    reslt.found = (reslt.found ? ' uses ' : ' does not use ') + 'our script!';
    console.log(reslt.page + reslt.found);//logs url does not use || uses our script
    phantom.exit();
});

And there is no output it just keeps running forever when i run it from php:

Test.php

<?php echo shell_exec('phantomjs hello.js');

?>

Answer 1

I'll post it here, too. Since I was the guy that put you on to phantomjs, it's only fair to provide you with, what I think, is the answer to your problems.
The following script opens a page in the headless phantom browser, logs any console messages that page would yield in an actual browser, (using the onConsoleMessage event), it also logs the error if the page were to be unable to load, and, if the page was opened without issues, it checks all <script> tags on that page, looking for your javascript file.

var page = require('webpage').create();
page.onConsoleMessage = function( message, line, srcId)
{//show console errors for page
    console.log('Page has errors showing in console: ' + msg
                + ' (line: ' + (line || '?') + ', id: ' + srcId + ')');
};
page.open('http://www.your-url-here.org',function(status)
{
    if (status != 'success')
    {//can't load page
        console.log('Failed to open page: ' + status);
        phantom.exit();
        return;
    }
    var reslt = page.evaluate(function()
    {
        var usesOurScript = false,
        scripts = document.querySelectorAll('script');//get all script tags
        /* Array.forEach is causing errors, as it turns out...
        Array.forEach.apply(scripts, [function(elem)
        {//check all loaded scripts
            if (/yourScriptName.js/.test(elem.getAttribute('src')))
            {//this src attribute refers your script
                usesOurScript = true;//set to true
            }
        }]);*/
        for (var i=0;i<scripts.length;i++)
        {
            if (/yourScriptName.js/.test(scripts[i].getAttribute('src')))
            {
                return {page: location.href, found: true};
            }
        }
        return {page: location.href, found: false};
    });
    //script was found? adjust message
    reslt.found = (reslt.found ? ' uses ' : ' does not use ') + 'our script!';
    console.log(reslt.page + reslt.found);//logs url does not use || uses our script
    phantom.exit();
});

If that file is does something like jQ (create a global reference to some object) you might even add this to the page.evaluate callback:

    var reslt = page.evaluate(function()
    {//this code will behave like it's running on the target page
        var libs = {jQuery: ($ || jQuery),
                    myLib: ourLibsGlobalName};
        return libs;
    });
    if (reslt.jQuery instanceof Object)
    {
        console.log('client uses jQ');
    }
    if (reslt.myLib instanceof Object)
    {
        console.log('client uses our lib, successfuly');//wouldn't be accessible if it contained errors
    }
    console.log(reslt.myLib);//shows full object, so you can verify it's the right one

Note:
This code is un-tested, I just wrote it off the top of my head. It may contain silly typo's. It's not a copy-pastable answer to all of your prayers.
I do believe the page.evaluate callback is able to return something, however: it's running in the context of the loaded page, and is sandboxed, so you may have to force an error:

page.evaluate(function()
{
    Array.forEach(document.querySelectorAll('script'), [function(elem)
    {
        if (/yourScript.js/.test(elem.getAttribute('src')))
        {
            throw {message: 'Script found',
                   nodeSrc: elem.getAttribute('src'),
                   pageUrl: location.href,
                   myLib  : yourGlobalVar}//<-- cf remarks on jQ-like usage
        }
    }]);
});

By throwing this custom error, which isn't being caught, so it'll end up in the console, you force the page.onConsoleMessage handler to deal with this exception. That could be a way around the sandbox restrictions, in a way, if they're causing the infinite loop issue to occur.