include php __DIR__
PHP scripts run relative to the current path (result of getcwd()),
not to the path of their own file.
Using __DIR__ forces the include to happen relative to their own path.
CORRECT: in file2.php: include (__DIR__ . "/file3.php");
To demonstrate:
- file1.php
- dir/
- file2.php
- file3.php
If file2.php includes file3.php like this: include `file3.php`.
It will work fine if you call file2.php directly.
However, if file1.php includes file2.php,
the current directory (getcwd()), will be wrong for file2.php,
so file3.php cannot be included.