> For the complete documentation index, see [llms.txt](https://bing.gitbook.io/phper/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bing.gitbook.io/phper/php/3.-kuang-jia/codeigniter/common.md).

# Common

```
function &is_loaded($class = '')
{
    static $_is_loaded = array();

    if ($class !== '')
    {
        $_is_loaded[strtolower($class)] = $class;
    }

    return $_is_loaded;
}
```