Passing php variable into Twig - Documentation throwing errors

Question

UPDATE: 1

I am using this method with DarkBee's help

$detect = new Mobile_Detect;
class Project_Twig_Extensions extends Twig_Extension{
    public function getFunctions(){
        return array(new Twig_SimpleFunction('detectDevice', function() use($detect){
            if($detect->isMobile()){
                return true;
            } else {
                return false;
            }
        }));
    }
}

I am calling it in Twig using

{% if detectDevice %}

There is no value being passes and the condition isn't being met so checking the documentation I wrote another method just in case https://twig.symfony.com/doc/2.x/advanced.html#functions

$twig = new Twig_environment($loader);
$function = new Twig_Function('detectDevice', function() use($detect){
    if($detect->isMobile()){
         return true;
    } else {
         return false;
    }
});
$twig->addFunction($function);

Which also passes no values, my 500 Server Errors have happily stopped thanks to DarkBee but i still can't seem to pass this properly into Twig.

Original Question

I am having immense trouble installing the brilliant Mobile_Detect plugin into my Opencart 3.0 project (https://github.com/serbanghita/Mobile-Detect) I have inserted it and successfully checked if the device is desktop or mobile within php.

I've learned in order to pass this php check into twig, i can either add it to global variables

  $twig = new Twig_Environment($loader);
  $mobTwig->addGlobal('isMobile', true);

or create a public function that extends twig

require_once(DIR_SYSTEM . 'detect/mobiledetectlib/Mobile_Detect.php');
$detect = new Mobile_Detect;
$detectFunction = new function(){
    if($detect->isMobile()){
       return true;
    } else {
       return false;
    }
}

class Project_Twig_Extensions extends Twig_Extension{
    public function getFunctions(){
        return array(new Twig_SimpleFunction('detectDevice', '$detectFunction'));
    }
}

Both options return a 500 Internal Server Error and immediately stop the page loading. For the last few days i cannot figure out why. No amount of googling has helped me. Does anyone have any insight why this might be happening?

Answer 1

You have quite some issues in the code you've posted:

1. Anonmynous functions

In PHP you can't instantiate a new function(), to define an anomynous function you just use this syntax

$foo = function() {
    return 'foo';
}
echo $foo(); //output: foo

2. Passing variables to an anomynous function

Inside you function $detectMobile you are trying to access the variable $detect, this variable however is not defined in the scope of the anomynous function.

To correctly use $detect inside your function you would need to use the language construct use.

$detectFunction = new function() use($detect) {
    if ($detect->isMobile()) return true;
    else return false;
}   

You could also use the global language construct but this is not recommended

$detectFunction = new function() {
    global $detect;
    if ($detect->isMobile()) return true;
    else return false;
}   

3. Passing the anomynous function

Don't use quotes to pass around variables of instances.

• Using new Twig_SimpleFunction('detectDevice', '$detectFunction') will tell twig to run the global function $detectFunction

• Using new Twig_SimpleFunction('detectDevice', "$detectFunction") will try to convert the anomynous function to a string. Which is not possible

The only correct way to pass the anonmynous function is just by passing the reference:

new Twig_SimpleFunction('detectDevice', $detectFunction)

Now if you combine everything you could become something like this

class Project_Twig_Extensions extends Twig_Extension{
    public function getFunctions() {
        $detect = new Mobile_Detect();

        return array(new Twig_SimpleFunction('detectDevice', function() use($detect) {
            if ($detect->isMobile()) return true;
            else return false;
        }));
    }
}

Or even better

class Project_Twig_Extensions extends Twig_Extension{
    protected $detect = null

    protected function getDetector() {
        if ($this->detect === null) $this->detect = new \Mobile_Detect();
        return $this->detect;
    }

    public function getFunctions() {

        return array(new Twig_SimpleFunction('detectDevice', function() {
            return $this->getDetector()->isMobile();
        }));
    }
}

---

On a lost note please make sure to show all errors while you are developing..