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I purchased a Drupal theme and the the support is...lacking. So I thought I'd try and tackle it myself. I'm relatively new to PHP programming, so please take it easy on me :)

The error I got was: Notice: Object of class Drupal\Core\Field\FieldItemList could not be converted to int in theme_css_alter()

Digging into the error, it came from the first line of code in this if statement:

if(isset($node->nid) && $node->nid == 90){
    //do stuff
 }

I did my research and found that its a PHP error when using the == operator, likely since $node->nid is being fetched as a string, and 90 is an integer, and it can't convert the nid on the fly.

Possible solutions I found while Googling were either making a 'getter' to fetch the nid as an integer (which sounds more complicated than necessary), using the === operator; and I'm guessing on my own that if I convert 90 to a string it would also work?

Now, doing a test run, === does stop the error from showing, but my research shows that === only works when both the value and type are equal, and given I'm comparing a string and an integer, I assume that it would always just be false then.

So...

  1. Am I correct in saying that in PHP 90 (as a string) does not == 90 (as an integer)?
  2. Am I correct in saying that using === instead of == is NOT the correct way to compare a string and integer?
  3. Would $node->nid == (string)90{ be the correct way to compare for this if statement? What is the most correct way to do this comparison?
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  • Comparing strings with numbers generally does what you expect. The error message indicates that $node->nid is a FieldItemList, not a string. Commented Feb 15, 2017 at 23:19
  • Thanks Barmar. I assumed nid would be a string because thats what it normally is elsewhere and that FieldItemList was just the PHP class in Drupal 8. Is that not correct either? Commented Feb 15, 2017 at 23:22
  • It might have a method to convert to a string, so you can use it where a string is needed, but it's not actually a string. Commented Feb 15, 2017 at 23:27

3 Answers 3

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When you compare a number with something else, the other thing is first converted to a number, and then these two numbers are compared. So a comparison like "90" == 90 does what you expect -- it's equivalent to 90 == 90.

The problem you're having is that $node->nid is not a string, it's an object of class Drupal\Core\Field\FieldItemList. The class doesn't provide a method to convert this type to a number, so it's not able to perform the comparison.

However, it appears that this type has a method to convert to string. But PHP won't do a double conversion when performing the comparison. So you need to perform the object->string conversion explicitly, and then PHP will convert the string to an integer.

if (isset($node->nid) && (string)$node->nid == 90)
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That sounds right. Thanks. I guess that makes it more of a Drupal thing than a PHP thing. I'm new here, should I change the question and open a new one at drupal.stackexchange.com?
I've just added a solution.
I've marked this as a solution since its technically correct with the questions I've asked. Unfortunately FieldItemList can't be converted to a string either, but now I know why this line is failing I can do some more digging. (FYI, I think the reason for my confusion is changes between Drupal 7 and 8; I think D7 you could call it with the solution you proposed...)
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A string will not be equal to an integer. You need to check for the type too. That is why we use the triple equal sign ===. Consider the following code:

$integer = 90;
$string = "90";

echo($integer == $string); // prints 1 (true)
echo($integer === $string); // prints 0 (false)

You can test your own variables in this page.

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Your code contradicts what you wrote in the answer. The first one prints true, showing that a string can be equal to an integer when you use ==.
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Barmar is correct on why this if statement is failing; the comparison is working but $node->nid is not a string or an integer. I'm adding this answer as additional reference for the Drupal side of things.

As reference: https://drupal.stackexchange.com/questions/145823/how-do-i-get-the-current-node-id

Drupal 8 has changed the way to access nid values. Ultimately, the reason is that the parameter is upcasted to a full node object when you try to access it, so its neither a string or integer.

The correct way to do the comparison would be to use either $node->nid->value or $node->id(). Alternative ways to fetch the id as a value are in the link.

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