thinkphp small problem, everybody help, thank you

$optstr =implode (', ', $array);
$where [' CID ']=array (' in ', $optstr);
I would like to ask the second sentence of the array () inside the ' in ' is what also mean, what role??? Thank you, sir.

Reply to discussion (solution)

Let's make a statement: I didn't use thinkphp.
Assuming your code is correct, he says:
In the final executed SQL instruction there is a component such as CID in (1,2,3,4)

is executed in parentheses.

Here in is actually the SQL keyword, just thinkphp encapsulated, and finally will parse into the most native SQL statement, you can use $model->getlastsql () to see the recent execution of a SQL to understand

In is the SQL statement in which your CID value can be a value in the $OPTSTR array

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