Add test to make sure that readonly properties cannot be reassigned by invoking the __clone() method directly

Zend/tests/readonly_props/readonly_clone_error6.phpt

@@ -0,0 +1,47 @@
+--TEST--
+Test that readonly properties cannot be reassigned by invoking the __clone() method directly
+--FILE--
+<?php
+
+class Foo
+{
+    public function __construct(
+        public readonly int $bar
+    ) {}
+
+    public function __clone()
+    {
+        $this->bar = 1;
+    }
+}
+
+$foo = new Foo(0);
+
+var_dump($foo);
+
+try {
+    $foo->__clone();
+} catch (Error $e) {
+    echo $e->getMessage() . "\n";
+}
+
+try {
+    $foo->__clone();
+} catch (Error $e) {
+    echo $e->getMessage() . "\n";
+}
+
+var_dump($foo);
+
+?>
+--EXPECTF--
+object(Foo)#%d (%d) {
+  ["bar"]=>
+  int(0)
+}
+Cannot modify readonly property Foo::$bar
+Cannot modify readonly property Foo::$bar
+object(Foo)#%d (%d) {
+  ["bar"]=>
+  int(0)
+}