WARNING: session_start(): open(write/session/..., O_RDWR) failed: No such file or directory

At the early stage of installation, you might get a long a cryptic message such as:

WARNING: session_start(): open(write/session//sess_rbl9peqhmppv03idn9ju8hqnv6, O_RDWR) failed: No such file or directory (2) line 290 (/var/www/includes/PHPDS.inc.php)WARNING: Unknown: open(write/session//sess_rbl9peqhmppv03idn9ju8hqnv6, O_RDWR) failed: No such file or directory (2) line 0 (Unknown)WARNING: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (write/session/) line 0 (Unknown)

It's because PHP can't write to the session folder. Usually simply because the "write" folder inside the main PHPDevShell folder is not writable. Please ensure the webserver can write inside it; the easiest way is to set the rights to 777. On linux, the command is:

chmod -R 777 /path/to/phpds/write