1. array_change_key_case :-
It changes all the keys of an array in uppercase.
<?php
$employee_id=array("Jim"=>"40535","Krish"=>"83007","Joe"=>"41233");
print_r(array_change_key_case($employee_id,CASE_UPPER));
?>
Output
Array ( [JIM] => 40535 [KRISH] ...
Anamika Gupta
Jul 23, 2018