Mysqli prepared statement with multiple values for IN clause

1. PHP 8.2 way. execute_query()
2. PHP 8.1 way. Array into execute()
3. Older versions, prepare/bind/execute way
4. Comments (5)

Before running any query with mysqli, make sure you've got a properly configured mysqli connection variable that is required in order to run SQL queries and to inform you of the possible errors.

Imagine you've got an array of values that you want to use in your SQL query.

PHP 8.2 way. execute_query()

Since PHP 8.2 you can use a handy function execute_query()

// INSERT example
$sql = "INSERT INTO users (email, password) VALUES (?,?)"; // sql
$mysqli->execute_query($sql,[$email, $password]); // in one go

In case your array has variable length, you need to create a list of placeholders dynamically

// WHERE IN example
$array = ['Nashville','Knoxville']; // our array
$parameters = str_repeat('?,', count($array) - 1) . '?'; // placeholders
$sql = "SELECT name FROM table WHERE city IN ($parameters)"; // sql
$result = $mysqli->execute_query($sql, $array); // in one go
$data = $result->fetch_all(MYSQLI_ASSOC); // fetch the data   

PHP 8.1 way. Array into execute()

Since PHP 8.1 you can pass an array directly to execute:

// INSERT example
$sql = "INSERT INTO users (email, password) VALUES (?,?)"; // sql
$stmt = $mysqli->prepare($sql); // prepare
$stmt->execute([$email, $password]); // execute with data! 

// WHERE IN example
$array = ['Nashville','Knoxville']; // our array
$parameters = str_repeat('?,', count($array) - 1) . '?'; // placeholders
$sql = "SELECT name FROM table WHERE city IN ($parameters)"; // sql
$stmt = $mysqli->prepare($sql); // prepare
$stmt->execute($array);
$result = $stmt->get_result(); // get the mysqli result
$data = $result->fetch_all(MYSQLI_ASSOC); // fetch the data   

Older versions, prepare/bind/execute way

For the earlier versions the task is a bit more elaborate.

// INSERT example
$sql = "INSERT INTO users (email, password) VALUES (?,?)"; // sql
$data = [$email, $password]; // put your data into array
$stmt = $mysqli->prepare($sql); // prepare
$stmt->bind_param(str_repeat('s', count($data)), ...$data); // bind 
$stmt->execute();

While There are several tricks that would help us with this challenge.

• First of all we will need to create a string with as many ? marks as many elements are in your array. For this we would use str_repeat() function which comes very handy for the purpose.
• Then this string with comma separated question marks have to be added to the query. Although it's a variable, in this case it is safe as its contents contains only constant values
• then this query must be prepared just like any other query
• then we will need to create a string with types to be used with bind_param(). Note that there is usually no reason to use different types for the bound variables - mysql will happily accept them all as strings. There are edge cases, but extremely rare. For the everyday use you can always keep it simple and use "s" for the everything.
• then we need to bind our array values to the statement. Unfortunately, you cannot just write it as a single variable, like this $stmt->bind_param("s", $array), only scalar variables are allowed in bind_param(). Luckily, there is an argument unpacking operator that does exactly what we need - sends an array of values into a function as though it's a set of distinct variables!
• the rest is as usual - execute the query, get the result and fetch your data!

Here is the code:

$array = [1,2,3]; // our array
$in  = str_repeat('?,', count($array) - 1) . '?';
$sql = "SELECT * FROM table WHERE column IN ($in)";
$stmt  = $mysqli->prepare($sql);
$types = str_repeat('s', count($array));
$stmt->bind_param($types, ...$array);
$stmt->execute();
$result = $stmt->get_result(); // get the mysqli result
$data = $result->fetch_all(MYSQLI_ASSOC); // fetch data