Question

I just saw this on php.net description of how key to value mapping works:

$switching = array(         10, // key = 0
                    5    =>  6,
                    3    =>  7, 
                    'a'  =>  4,
                            11, // key = 6 (maximum of integer-indices was 5)
                    '8'  =>  2, // key = 8 (integer!)
                    '02' => 77, // key = '02'
                    0    => 12  // the value 10 will be overwritten by 12
                  );

I just cant quite understand how 11 could be assigned key 6. I know 5 is not possible since it is already used on the second element as a key so it makes sense to jump it over.

But should not be 11 intuitively assigned key 4 in the first place since the first element of the array 10 is assigned key 0 and therefore the key value is incremented 0..1..2..3..4 from that point according to the first index unless specified otherwise (e.g 5=>6 could have had key 1, 3=>7 with key 2, and ‘a’=> 4 could have had key 3 if not specified)? And also, why does it say that 11 should be assigned a key that represents the maximum integer of indices (in this case 6 since 5 was used already)?

Would appreciate any help/clarification. Please let me know if the question needs to be clarified. Thanks much.

Answer 1

It is implemented in this way just because it is the most performant solution – to just use maximum_specified_key + 1, rather than to find a hole in enumration