Fix refcount mistake in \Io\Poll\Backend::getAvailableBackends()

Author: ndossche

ext/standard/io_poll.c

@@ -414,7 +414,7 @@ PHP_METHOD(Io_Poll_Backend, getAvailableBackends)
 		if (php_poll_is_backend_available(backends[i])) {
 			const char *name = php_io_poll_backend_type_to_name(backends[i]);
 			zval enum_case;
-			ZVAL_OBJ(&enum_case, zend_enum_get_case_cstr(php_io_poll_backend_class_entry, name));
+			ZVAL_OBJ_COPY(&enum_case, zend_enum_get_case_cstr(php_io_poll_backend_class_entry, name));
 			add_next_index_zval(return_value, &enum_case);
 		}
 	}

ext/standard/tests/poll/poll_backend_getAvailableBackends.phpt

@@ -0,0 +1,12 @@
+--TEST--
+\Io\Poll\Backend::getAvailableBackends() - loop
+--FILE--
+<?php
+$objs = [];
+foreach (($expr1 = \Io\Poll\Backend::getAvailableBackends()) as $expr2) {
+    $objs[] = $expr2;
+}
+echo "Okay\n";
+?>
+--EXPECT--
+Okay