usort RC1

Author: nielsdos

ext/standard/array.c

@@ -906,8 +906,11 @@ static void php_usort(INTERNAL_FUNCTION_PARAMETERS, bucket_compare_func_t compar
 		RETURN_TRUE;
 	}
 
-	/* Copy array, so the in-place modifications will not be visible to the callback function */
-	arr = zend_array_dup(arr);
+	/* Copy array, so the in-place modifications will not be visible to the callback function.
+	 * Unless there are no other references since we know for sure it won't be visible. */
+	if (!zend_may_modify_array_in_place(array)) {
+		arr = zend_array_dup(arr);
+	}
 
 	zend_hash_sort(arr, compare_func, renumber);