How can we determine whether a PHP variable is an instantiated object of a certain class?

instanceof is used to determine whether a PHP variable is an instantiated object of a certain class.

<?php
class MyClass
{
}
class NotMyClass
{
}
$a = new MyClass;
var_dump($a instanceof MyClass);
var_dump($a instanceof NotMyClass);
?>

output:

bool(true)
bool(false)