How to Correctly Use the IN Operator with MySQLi Prepared Statements and Multiple Parameters?

Using IN Operator with MySQLi Prepared Statements

When using the IN operator with IN operator in MySQLi prepared statements, it is crucial to properly format the parameters. The initial code provided:

$data_res = $_DB->prepare('SELECT `id`, `name`, `age` FROM `users` WHERE `lastname` IN (?)');
$data_res->bind_param('s', $in_statement);

involves an error because $in_statement is a string rather than an array of values. To resolve this issue, an alternative approach using the call_user_func_array function is presented:

$int = str_repeat('i', $count_params);
array_unshift($arParams, $int);

$q = array_fill(0, $count_params, '?');
$params = implode(',', $q);

$data_res = $_DB->prepare('SELECT `id`, `name`, `age` FROM `users` WHERE `lastname` IN ('.$params.')');
call_user_func_array(array($data_res, 'bind_param'), $arParams);

In this modified code:

• $count_params determines the number of parameters to be passed.
• str_repeat('i', $count_params) creates a string of i characters equal to the number of parameters, representing the data type for each parameter.
• array_unshift($arParams, $int) prepends the data type string to the $arParams array.
• array_fill(0, $count_params, '?') generates a string of question marks for the IN clause.
• call_user_func_array is used to bind multiple parameters simultaneously, passing the $arParams array as an argument.

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