PHP函数调用在另一个文件里

function __shop($fruits,$greens,$cosmetics)
{
$shop1 = 'shop1.txt';

            if (file_exists($shop1)) {
                echo "The file {$shop1} exists";
            } else {
                echo "The file {$shop1} does not exist";
            }

这个怎么调用？？谢大神

    }

是PHP文件，直接#include_once "函数文件名.php"