You can also use:

<?php 
$myarray = [
"Orange",
"572" => "Banana",
"omg" => "Chili",
"nevermind" => "mango"
];

$myarray[0] = "NO-Orange"; 
$myarray["572"] = "BANANAPHONE!!!";
$myarray["omg"] = "NO-Chili";

print_r($myarray);

?>

RESULT:
Array
(
    [0] => NO-Orange
    [572] => BANANAPHONE!!!
    [omg] => NO-Chili
    [nevermind] => mango
)

with regards