insert multiple values into multiple rows with prepared statement PHP, MYSQL

Question

I'm trying to insert data from a multiselect into a database with multiple rows.

I once managed to insert them all into ONE row, each with a comma which is not really good from the database perspective. The data from the multiselect is stored as an array in a variable, which then should be filled into multiple rows in the database with a foreach loop.

$array = implode((array)$_POST['multiselectdata']);

$sql = "INSERT INTO tbl_example (column1, column2) VALUES (?, ?)";

$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)){
    ....
    exit();
}
else {
    mysqli_stmt_bind_param($stmt, "ii", $array, $id);
    mysqli_stmt_execute($stmt);
    $result= mysqli_stmt_store_result($stmt);
    mysqli_fetch_all($result,MYSQLI_ASSOC);
    foreach($result as $row){
        echo $row["column1"];
    }
    exit()
}

As a result in each row there should be 1 value displayed of the array in column1 and in column2 there is always going to be the same id. Currently this only inserts 1 value into the database and only 1 row

Answer 1

Rather than implode the contents of $_POST['multiselectdata'] you can iterate over it as an array and execute your prepared statement for each value in the array:

$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)){
    // ....
    exit();
}
else {
    mysqli_stmt_bind_param($stmt, "ii", $value, $id);
    foreach (explode(',', $_POST['multiselectdata']) as $value) {
        mysqli_stmt_execute($stmt);
    }
}

Note that calling mysqli_stmt_store_result on an INSERT query makes no sense as there is no result set. That line and the foreach loop following should be removed from your code.