mysql update data entry in column without removing previous data

Question

What I'm trying to achieve is whenever this column is updated, it shouldn't remove the previous data that has been filled, instead, it should just enter data in the next line with the previous data too.

For example

• Author 1
• Author 2

This is my code

$booktb = $db->update("books", "author" => $author); 

I've looked into this question but it didn't work for me Update data in mysql column field without removing previous value

Answer 1

pseudo code

$b = $db->select("books","author" => "kafka"); 

$b["title"] =  "another book"

$db->insert("books",$b);