mysqli::query(): Couldn't fetch mysqli

Probably somewhere you have DBconnection->close(); and then some queries try to execute .

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Hint: It's sometimes mistake to insert ...->close(); in __destruct() (because __destruct is event, after which there will be a need for execution of queries)

Reason of the error is wrong initialization of the mysqli object. True construction would be like this:

$DBConnect = new mysqli("localhost","root","","Ladle");

I had the same problem. I changed the localhost parameter in the mysqli object to '127.0.0.1' instead of writing 'localhost'. It worked; I’m not sure how or why.

$db_connection = new mysqli("127.0.0.1","root","","db_name");

Hope it helps.