Are there the same values ​​in the array?

Question

PHP

How to find out if there are identical values ​​in an array? We just need a logical answer at the output IS or NO. "0" or "1". No need to look for exactly what value is repeated, it is not important within the framework of this task. Thanks in advance!

EXAMPLE:
$a = "1";
$b = "2";
$c = "3";
$d = "4";
$e = "1";

$arr = [$a, $b, $c, $d, $e]