Description:
------------
The same call to get_class_vars() prints different values depending if it's the first time I run it, or if it's subsequent times, when opcache is on which is on by default. (See code in Test script)

First time, e.g. http://localhost/mytest.php, it prints:

7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => b
)

Refresh the page, now prints:

7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => a
)

Any subsequent refreshes prints [v] => a

Now slightly modify the PHP page to trigger a change , and it prints:

7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => b
)

Refresh the page, and goes back to:

7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => a
)

And subsequent refreshes still print [v] => a

SOLUTION: 

Set opcache.enable=0 in php.ini, restart apache2. Bug disappears, and prints [v] => b each time now. 

VERSIONS:

Apache/2.4.41 (Ubuntu)
PHP 7.4.3 (cli)
libapache2-mod-php 2:7.4+75

Test script:
---------------
class MyClass {
    public static $v = 'a';
}

echo '<pre>';
echo phpversion() . "\n";
print_r(get_class_vars('MyClass'));
MyClass::$v = 'b';
print_r(get_class_vars('MyClass'));

Expected result:
----------------
7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => b
)

Actual result:
--------------
7.4.3
Array
(
    [v] => a
)
Array
(
    [v] => a
)

// Note, it is correct only first time it is run, but wrong all subsequent times, when opcache is active