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static::class cannot be used for compile-time class name resolution

Description

static::class resolves to the class name of whichever subclass is actually in scope at runtime, through late static binding. A class constant, on the other hand, is resolved once and shared identically by the declaring class and every class that inherits it, so it cannot hold a value that is meant to vary per subclass. self::class is accepted in the same spot because it never varies.

Example

<?php

class Base {
	const NAME = static::class;
}

?>

Alternatives

  • Use self::class if a fixed class name is acceptable.
  • Expose it through a method instead: public static function name(): string { return static::class; }.

Changed Behavior

This error may appear following an evolution in behavior, in previous versions. See