Symbol implementation

ES6 supports the Symbol type that is a replacement to hard-coded identifiers where it are not really need. I like to suggests a similar feature to PHP. #0: it should be a partial class that could not be instantiated (new symbol should be invalid, like an abstract class). In this point I should suggests two options: 1. It should works like a new keyword "symbol", but that could be extended like a class when need. (It will make sense on item #2). But could be referenced directly without need of the ::class. (eg. $a = symbol;). 2. Other option is use it as a new keyword "symbol" followed by a \Symbol reference class (like "instanceof Class" works). Eg. $a = symbol \Symbol; Anyway, maybe \Symbol could works as a default type, so only $a = symbol could be do the job. Or even consider symbol as a language constructor, allowing symbol(\Symbol), for instance. Ok, now to all make senses (I do expects), keep reading... (I will use otpion 2 as reference for now) #1: It could be used to fill constants, for instance, with "magic identifiers" that have no real value, needly. Eg.: public const USER_NOT_FOUND = symbol(), USER_INVALID = symbol(); Where USER_NOT_FOUND !=/!== USER_INVALID. #2: Another possibility is to extends it as an class, so it could be used as parameter typehint: (not available on ES6, I guess) class UserErrorSymbol extends \Symbol {} public const USER_NOT_FOUND = symbol(UserErrorSymbol), USER_INVALID = symbol(UserErrorSymbol); public function setError(UserErrorSymbol $error) {...} #3: it should have a fallback name (storing a scalar value), so in case you need to persist it (or serialize), so you could give a name: public const USER_NOT_FOUND = symbol(UserErrorSymbol as "UserNotFound"), USER_INVALID = symbol(UserErrorSymbol as "UserInvalid"), USER_INVALID_B = symbol(UserErrorSymbol as "UserInvalid"); symbol_alias(USER_INVALID) === 'UserInvalid' (string) USER_INVALID === 'UserInvalid' USER_INVALID !=/!== USER_INVALID_B #4: it could be used as a kind of anonymous array or object key: $arr[symbol()] = 1; $arr[symbol()] = 2; count($arr) === 2 $obj->{symbol()} = 1; $obj->{symbol()} = 2; count(get_object_vars($obj)) === 2 But symbol could not be accessed without a valid reference: echo $arr[symbol()]; // error: index symbol() is undefined or maybe symbol type could not be used directly to read an array value $symbol = symbol(); $arr[$symbol] = 1; echo $arr[$symbol]; // print 1 It is just a draft, but I do belive that it will be a good feature for PHP.