Question

I am wrote an array for all months in a year as follows:

$MNTH["01"] = "January";
$MNTH["02"] = "February";
$MNTH["03"] = "March";
$MNTH["04"] = "April";
$MNTH["05"] = "May";
$MNTH["06"] = "June";
$MNTH["07"] = "July";
$MNTH["08"] = "August";
$MNTH["09"] = "September";
$MNTH["10"] = "October";
$MNTH["11"] = "November";
$MNTH["12"] = "December";

When I do a variable dump on the keys of $MNTH with var_dump(array_keys($MNTH)),
I get:

array(12) {
 [0]=> string(2) "01"
 [1]=> string(2) "02"
 [2]=> string(2) "03"
 [3]=> string(2) "04"
 [4]=> string(2) "05"
 [5]=> string(2) "06"
 [6]=> string(2) "07"
 [7]=> string(2) "08"
 [8]=> string(2) "09"
 [9]=> int(10)
 [10]=> int(11)
 [11]=> int(12) }

I was expecting strings for the last three keys. How did it become integer? What should I do to correct this phenomenon?

Answer 1

PHP converts numeric keys to integers at the time you create the array element. It isn’t array_keys that is doing it. But there is a hack to get string numeric keys:

$a = new stdClass;
$a->{"0"} = "zero";
$a = (array) $a;
var_dump($a);

Output:

array(1) {
  ["0"]=>
  string(4) "zero"
}

But you won’t be able to access that key by subscript, so it’s not very useful.

If you must have string keys, you’ll need to prefix them with another non-numeric (or zero) character:

$MNTH["001"] = "January";
$MNTH["012"] = "December";

From the documentation:

A key may be either an integer or a string. If a key is the standard representation of an integer, it will be interpreted as such (i.e. “8” will be interpreted as 8, while “08” will be interpreted as “08”). Floats in key are truncated to integer. The indexed and associative array types are the same type in PHP, which can both contain integer and string indices.