PHP InstanceOf works locally but not on host server - php-7

Question

I have an issue with PHP 7's instanceof statement that is only happening on certain conditions.
It seems that instanceof works locally on my dev machine (MAMP Pro running PHP 7.0.13) but not on my Hosted Server (HostEurope, PHP 7).
I have tried the following :
downgrading to PHP 5.6
using is_a instead
Using fully qualified name e.g. \Site\Ad
but they all exhibit the same behaviour.
I've tried Googling "PHP instanceof not working" and variations of it but I haven't found anything relevant.
I was wondering if anyone had experienced something similar or possible solutions to try?
The Code in question is:
<?php
namespace Site;
require_once(__DIR__."/../interface/IOutput.php");
require_once(__DIR__."/../lib/Lib.php");
require_once(__DIR__."/../site/AdMediumRectangle.php");
require_once(__DIR__."/../site/AdSnapBanner.php");
require_once(__DIR__."/../const/Const.php");
class AdFactory
{
/**
* Define(AD_BANNER, 0);
* Define(AD_RECTANGE, 1);
* Define(AD_SUPERBANNER, 2);
* Define(AD_SKYSCRAPER, 3);
**/
/**
* #param $object
* #return AdMediumRectangle|AdSnapBanner|string
*/
public static function CreateObject($object)
{
$ad = wire(pages)->get("/ads/")->children->getRandom();
if ($ad == null)
return new \Exception("No Random Ad found");
switch ($object) {
case AD_BANNER:
echo "AD_Banner Selected\r\n";
$adSnapBanner = new AdSnapBanner($ad);
return $adSnapBanner;
break;
case AD_RECTANGLE:
echo "AD Rectangle Created\r\n";
$adRectangle = new AdMediumRectangle($ad);
return $adRectangle;
break;
case AD_SUPERBANNER:
case AD_SKYSCRAPER:
default:
echo "AdFactory BlankObject created";
return "";
break;
}
}
public static function Markup($object)
{
$obj = AdFactory::CreateObject($object);
if (($obj instanceof AdSnapBanner) || ($obj instanceof AdMediumRectangle)) {
echo "InstanceOf worked";
return $obj->Markup();
}
else {
echo "return blankString";
return "";
}
}
}
Update : This is the code that calls the above AdFactory class
<?php
namespace Site;
require_once(__DIR__."/../interface/IOutput.php");
require_once(__DIR__."/../lib/Lib.php");
require_once(__DIR__."/../factory/AdFactory.php");
require_once (__DIR__."/../const/Const.php");
class AdInjector
{
public static function Inject($page, $ad_pos)
{
//Select an Ad from /Ads/ according to criteria
//$ads = wire(pages)->get("/ads/")->children;
$count = 1; //$ads->count();
if ($count > 0) {
$mod = $page->id % 3;
echo "mod=" . $mod . "\r\n";
if ($mod == $ad_pos) {
switch ($mod) {
case AD_POS_TITLE;
case AD_POS_BANNER:
//Pick an Snap Banner
echo "Banner Injected (banner):" . AD_BANNER . "\r\n";
return AdFactory::Markup(AD_BANNER);
break;
case AD_POS_SIBLINGS:
echo "Banner Injected (rect):" . AD_RECTANGLE . "\r\n";
//Pick an Ad Rectangle
return AdFactory::Markup(AD_RECTANGLE);
break;
default:
return "";
break;
}
} else
return "";
} else
return "";
}
}

Answer 1

instanceof is a language construct which is so essential to PHP that it is de facto impossible not to work properly.
The code you provided is not enough to tell where the issue might be happening.
Chances are, you have a folder not readable on your online server and simply get somewhere a null value instead of an expected object along your code. Ask yourself: "If it is not the object I expect, what else is it?"
Use var_dump() or printf() to investigate what your variables actually contain and you will find the error soon.
For your code, PHPUnit tests would be a benefit, or at least the use of assert() here and there in your code.

Answer 2

Turns out there was a bug in 1 of the API calls I was making to the Processwire CMS.
$ad = wire(pages)->get("/ads/")->children->getRandom();
And my local and server instance of Processwire was not the same version, which was news to me. I normally have it synchronised, including any modules I use.
I also suspect my null check is not correct PHP, to add to the problem.

Answer 3

It has to do with namespaces used in the code:
Locally (Code with no namespaces) I used this, working fine:
if ($xmlornot instanceof SimpleXMLElement) { }
But on the server (code with namespaces) only this worked:
if ($xmlornot instanceof \SimpleXMLElement) { }
See also this question/answer: instanceof operator returns false for true condition