relative path, php getcwd

# one level up current dir

cd ..

# equivalent 

cd ./..

# This means .. is used after directory

# one levelup of /home/test/dir and go to /home/test/vendor

cd /home/test/dir/../vendor

#PHP working directory is the directory where you run the script

echo getcwd();

# If you run the script /home/test/myscript.php, working directory is /home/test

# If you have a file in /home/test/function/test.php, and you have another file in /home/test/vendor/myscript.php

# in /home/test/function/test.php, require_once '../vendor/myscript.php' will not work, because curretn working directory is /home/test. One level up that is /home, and there is no such thing as /home/vendor 

#solution

require_once __DIR__ . '/../vendor/myscript'

__DIR__ is current directory of file so /home/test/function, so /../ means one level up that means /home/test, then /home/test/vendor

https://stackoverflow.com/questions/14184223/using-require-once-for-up-directory-not-working

https://stackoverflow.com/questions/5318202/file-path-in-php-require