为什么file_exists总是返回false？

Question

When using file_exists(), it always returns false. But the file actually exists and can be loaded using require. This is my code:

// Creating dependency lists.
$data_dependency = array("mysql", "oracle", "postgresql", "sqlite", "access");

// Calling the dependecny files.
foreach ($data_dependency as $list) {
    $list = "class.data.$list.php";
    _system::debug("Calling required class $list ...");

    if (file_exists($list)) {
        include($list);
        _system::debug("Calling $list was successfull.");
    } else {
        _system::debug("Calling $list was failed. Now we close the system load.");
        exit("Calling $list was failed. Now we close the system load.");
    }
}

When I load the page, the page always exit(). I think the reason is the file_exists() function always return false.

Answer 1

$list in your foreach loop might be set incorrectly. Have you tried $list="class.data.".$list.".php"; ?