What do I do if the PHP array is the MySQL query condition where xx in array?

Ask the PHP array as the MySQL query condition where xx in array, how to handle
Originally think of the array $customerid split out, to determine the length of different variables, the number of variables to be judged, and then write the bottom of the MySQL query, some trouble, ask there is no good way, thanks!

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$customerid:

Array (size=2)
0 = String ' 5 ' (length=1)
1 = String ' + ' (length=2)
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$customer->where ("id in". $customerid)->count (); That's the point, of course, it's not right to put the array directly here.
------to solve the idea----------------------
The first question, if it is to check the single ID, the direct id = XX can be, no need to use in
If you want to check multiple IDs, combine the array with the IMPLODE function into the ID in (1, 2, 3) string of this format
The last question, if your requirement is to output a list of users, and output each of the top 10 favorites, you should consider caching

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