PHP: insert into associative array by index?

I have an array like:

$example = array("car"=>"red", "banana"=>"yellow", etc...)

Is it possible to alter a value of the array by index instead of key value like

$example[0] = "blue";

So that the 开发者_运维知识库array now looks like

$example = array("car"=>"blue", "banana"=>"yellow", etc...)

---

you can do this way:

$e = array("car"=>"red", "banana"=>"yellow");
$keys = array_keys($e);
$e[$keys[0]] = 'blue';

var_dump($e);

the output is

array(2) { ["car"]=> string(4) "blue" ["banana"]=> string(6) "yellow" }