(PHP 8 >= 8.1.0)
ReflectionEnum::hasCase — Checks for a case on an Enum
$name): boolDetermines if a given case is defined on an Enum.
nameThe case to check for.
   true if the case is defined, false if not.
  
Example #1 ReflectionEnum::hasCase() example
<?php
enum Suit
{
    case Hearts;
    case Diamonds;
    case Clubs;
    case Spades;
}
$rEnum = new ReflectionEnum(Suit::class);
var_dump($rEnum->hasCase('Hearts'));
var_dump($rEnum->hasCase('Horseshoes'));
?>
The above example will output:
bool(true) bool(false)