When PHP array keys are printed in descending order, only one?

{Code ...}

php
  "36","Bill"=>"35","Peter"=>"43");krsort($age);foreach($age as $x=>$x_value)    {    echo "Key=" . $x . ", Value=" . $x_value;    echo "
";    }?>

Reply content:

php
  "36","Bill"=>"35","Peter"=>"43");krsort($age);foreach($age as $x=>$x_value)    {    echo "Key=" . $x . ", Value=" . $x_value;    echo "
";    }?>

I changed the sorting by value just now. No problem,
Must all keys (including databases) be unique?

I thought it was a sorting function problem. It turned out to be an array definition problem. The subject prints the size of your array and there are only two elements:

php$age=array("Bill"=>"35","Bill"=>"32","Peter"=>"43");echo count($age);# > 2

If there are two identical key values in the array, then you want $ age ["Bill"] (assuming the values of these two keys are different) Which one should output?

So this is not a problem with sorting functions. Therefore, the keys in the array must be unique. Otherwise, confusion may occur.

PHP defines an array. The key is unique. If two identical indexes are displayed. Add and overwrite the previous one.
For details, see:
Http://php.net/manual/zh/function.array.php