Absolutely! However, we must be careful not to define it in a too predictable way lest we violate the Principle of Most Surprise.

php_real_equivalence_4()

Exactly!

But it must invoke with additional NULL-parameter to achieve real effect and analyse return value for TRUE, FALSE, NULL:

  php_real_equivalence_4($x, $y, null);

Except they had to call it php_real_equivalnce_4() because php_real_equivalence_4() was taken.