There is no space available in the disk

There is no space available in the disk

There may be a file that would have been using the whole space, that may be a log file. if error logging occurs in an a loop for infinite times then it can fill up the drive fleetly. Files may be deleted as it generally happens due to rotation of logs, floundering to re-continue the service that is writing them. it can furthermore consume space and amplify until the program that has it open it or abdicates.
the lsof commands can give list of open files,accommodating deleted files.

I think owa has a 2.5 GB limit on its PST file. You might  have beaten that limit. You should  scrutinize  scrolling  some old emails off.

If you are using Exchange then this error should not be possible unless you are running out of room on your server. It can be your ISP which is not allowing you too much space. If so use the suggestion I just gave you.

Or you can target the PHP skill and you can fix it
a long-running PHP script, rather than a PHP web page. "ps -A v" might tell you the full command line, including which script is responsible, if you haven't killed it already