Data detail from full calendar event click

First of all apologies. I feel that I am posting questions almost every day which must be tiresome for all.

So I have my full calendar with bookings and on click, I want to go to a detail page.
I use the event click, set a variable to the id of the event, and add the variable to the URL to retrieve the record.

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The ‘where’ clause in the query is set to $_GET (the page will be an admin page and secure) to retrieve more details of the booking.

Screenshot 2021-03-02 at 12.48.31950×121 14.3 KB

But the $_GET clause is not “getting through”. I have a set value ‘get_id’ to check.

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As usual, any advice, suggestions, and comments gratefully received.