PHP: Count an ArrayAccess object without Countable

Question

So I'm working with some external PHP code that I don't have the full source for. I am using reflection to work out callable methods, etc.

They have a class like so:

class SpecialArray implments \ArrayAccess
{
 public function offsetExists($index){}
 public function offsetGet($index){}
 public function offsetSet($index, $value){}
 public function offsetUnset($index){}
}

So logically I can foreach(SpecialArray), that's fine.

However in the code I can somehow do count(SpecialArray) and get the correct count, eg if there are 5 elements in the SpecialArray doing count(SpecialArray) will return 5!

However there isn't a count method in the class, nor does the class implement Countable Calling SpecialArray->count() also fails with Call to undefined method

Does anyone have any ideas how they may be doing this voodoo magic??

Full \ReflectionClass::export()

Class [ class ThirdParty\SpecialArray implements ArrayAccess ] {
 - Constants [0] {
 }
 - Static properties [1] {
 Property [ public static $_metadata ]
 }
 - Static methods [1] {
 Method [ static public method &getMetadata ] {
 - Parameters [0] {
 }
 }
 }
 - Properties [0] {
 }
 - Methods [5] {
 Method [ public method offsetExists ] {
 - Parameters [1] {
 Parameter #0 [ $index ]
 }
 }
 Method [ public method offsetGet ] {
 - Parameters [1] {
 Parameter #0 [ $index ]
 }
 }
 Method [ public method offsetSet ] {
 - Parameters [2] {
 Parameter #0 [ $index ]
 Parameter #1 [ $value ]
 }
 }
 Method [ public method offsetUnset ] {
 - Parameters [1] {
 Parameter #0 [ $index ]
 }
 }
 Method [ public method fetch ] {
 - Parameters [1] {
 Parameter #0 [ $index ]
 }
 }
 }
}

• vichu: why don't you manually count if you can loop in it ??
• M. Eriksson: Out of curiosity, how do you work with external PHP code you don't have the source for?
• Don't Panic: The correct count doesn't happen to be 1, does it?
• Philipp Palmtag: If it is 1 we know the answer ;)
• cosmorogers: @MagnusEriksson with difficulty...

Answer 1

After testing your code, I got the return value of 1. Let me quote the PHP manual of count():

Returns the number of elements in array_or_countable. When the parameter is neither an array nor an object with implemented Countable interface, 1 will be returned. There is one exception, if array_or_countable is NULL, 0 will be returned.

As of PHP 7.2, trying to use count() on something uncountable will give a Warning, such as

Parameter must be an array or an object that implements Countable

Demo https://3v4l.org/G0pR3

• cosmorogers: Thanks for the answer, but count(SpecialArray) is returning the correct count, eg if there are 7 elements in the SpecialArray (that I can loop over in a foreach, etc), count(SpecialArray) returns 7!!!!
• Philipp Palmtag: Do you have more code for us. Like that we wont get far.