PHP 7: Function which creates different classes with "new class" - php-7

Question

If I create a class with PHP7 multiple times, it seems it is returning always the same class instead of returning a new one each time.
For example:
function createAClass()
{
return new class
{
public static $foo=0;
};
}
$class = createAClass();
$class::$foo = 3;
echo "class:".$class::$foo."<br>";
$anotherClass = createAClass();
echo "anotherClass:".$anotherClass::$foo."<br>";
This is the output:
class:3
anotherClass:3
I though the output should be 3 and 0. What's happening? Is this a bug, or a "feature" of PHP 7? :)
btw, I was trying to use this to test a trait with static methods with PHPUnit.

Answer 1

I've found the documentation and it seems it is the expected behaviour:
http://php.net/manual/en/language.oop5.anonymous.php
All objects created by the same anonymous class declaration are instances of that very class.
But I needed to create a function which returned a different class each time it was called, so I came with this solution:
function createAClass()
{
$class = null;
$stamp = random_int(PHP_INT_MIN ,PHP_INT_MAX);
echo "stamp: $stamp\n";
$classcode = <<< EOT
\$class = new class {
public static \$differentiate='$stamp';
// YOUR CODE HERE
};
EOT;
echo "Source code of class:\n$classcode\n\n";
eval($classcode);
return $class;
}
$class = createAClass();
$anotherClass = createAClass();
if (get_class($class) === get_class($anotherClass)) {
echo 'same class';
} else {
echo 'different class';
}