Description:
------------
In PHP 7.4 class_exists($c, true) can return false and class_exists($c, false) can return true in one moment.



Test script:
---------------
file classes.php:
-----

<?php

class C1
{
	function f($arg)
	{
	}
}

class C2 extends C1
{
	function f()
	{
	}
}
?>


file test.php:
-------

<?php

set_error_handler(function () {
	var_dump(class_exists('C2', true)); // returns false
	var_dump(class_exists('C2', false)); // returns true
});

include 'classes.php';

?>

Expected result:
----------------
Both return the same value.

Actual result:
--------------
var_dump(class_exists('C2', true)); // returns false
var_dump(class_exists('C2', false)); // returns true