is_a() Versus Instanceof

<?php

class A {}

var_dump(new a instanceof A);
// true

var_dump(new a instanceof A::class);
// Fatal error

var_dump(is_a(new a, A::class));
// true

var_dump(is_a(new a, A);
// Undefined constant A

is_a() and instanceof are the same feature: check if an object is of a specific class. Yet, they do things in different ways.

Using the ::class operator is safe in both cases.

Using a name is a class name for instanceof, while it is a constant name with is_a(). This may lead to confusion.

See Also

• is_a (PHP manual)
• type operators (PHP manual)
• is_a and instanceof are in a boat… [Try me]

PHP Features

• type
• instanceof
• is_a

Last updated: 10 September 2026