The above function looks fine, and I tested it just to be sure. It may be that you don’t like what you’re getting.
It adds user meta to the particular author with key Points and value 100, like so:
[Points] => Array
(
[0] => 100
)
On the second publish, it will produce the following:
[Points] => Array
(
[0] => 100
[1] => 100
)
And so on.
If you want any other results, then you’ll need to adjust parameters or create a function to process the results.
For example, if you wanted to “add” 100 points arithmetically every time – so the second publish produces the value “200,” the third “300,” and so on – you’d need to get the user_meta, if any, and then arithmetically add each new value, then update the old value with the sum – not simply programmatically “add” the new value to the array.
Alternatively, you could add whatever values together, or turn them into sub-arrays with additional info (whatever other $post values you wanted to save).