Create Random Serial with PHP

I want to have a random serial created on my website everytime someone visits.

The format of the serial should be XXXXX-XXXXX-XXXXX-XXXXX.

X represents a random number or capital letter.




Unfortunately I have no idea how to do this. Could anybody please help me out?

So for example the random serial output could be: 3WT4A-NB34O-JU87P-B3UHS




Thanks a lot!

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