PHP Enum as Class

php_enum_as_class.php

<?php

namespace Earth;

class Enum {
    protected string $constName;
    
    public function __construct(string $constName) {
        $this->constName = $constName;
    }
    
    public function __toString() {
        try {
            return self::getConstants()[$this->constName];
        }
        catch(\Throwable $ex) {
            return 'unknown';
        }
    }
    
    public static function equals(Enum $a, Enum $b) {
        return (string)$a === (string)$b;
    }
    
    public function is(Enum $b) {
        return (string)$this === (string)$b;
    }
    
    public static function __callStatic($method, $args) {
        if(in_array($method, array_keys(self::getConstants()))) {
            $calledClass = self::getClass();
            return new $calledClass($method);
        }
        
        throw new \Exception(sprintf("`%s` is not a %s.", $method, get_called_class()));
    }
    
    protected static function getConstants() {
        return (new \ReflectionClass(self::getClass()))->getConstants();
    }
    
    protected static function getClass() {
        return get_called_class();
    }
}

class TemperatureEnum extends Enum {
    public const COLD = 'cold';
    public const HOT = 'hot';
}

$cold = TemperatureEnum::COLD();
$hot = TemperatureEnum::HOT();

echo $cold; // echoes "cold"
echo $hot; // echoes "hot"
//echo TemperatureEnum::Unknown(); // throws "`Unknown` is not a Earth\TemperatureEnum"

var_dump([
    $cold == $hot,                              // false
    $cold == TemperatureEnum::COLD(),           // true
    $cold === TemperatureEnum::COLD(),          // false
    Enum::equals($cold, TemperatureEnum::COLD()),   // true
    $cold->is(TemperatureEnum::COLD())          // true
]);