如何在PHP中正确比较字符串和整数？

Question

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?

Answer 1

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)