<?php

$myArray = [
        "fname" => "Sudhir",
        "lname" => "Gour",
        "age" => 27,
        "city" => "Jaipur",
        "state" => "Jaipur",
        "country" => "India"
    ];
    
print_r(array_change_key_case($myArray , CASE_UPPER));