PHP插入HTML表单值通知数组到字符串的转换

Question

I have a notice when I'm try to insert form values to database:

Array to string conversion in C:\\path\\rangking.inc.php on line 41

I've read this answer but I have a different array that showing with print_r is:

Array ( [ia] => 6 [ik] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 ) [nn] => Array ( [0] => 80 [1] => 79 [2] => 79 [3] => 80 ) ) 1

any suggesting answer would be appreciate

form HTML :

    if($_POST){

    include_once 'includes/rangking.inc.php';
    $eks = new rangking($db);

    $eks->ia = $_POST['ia'];
    $eks->ik = $_POST['ik'];
    $eks->nn = $_POST['nn'];

    if($eks->insert2()){
?>
<div class="alert alert-success alert-dismissible" role="alert">
  <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
  <strong>Berhasil Tambah Data!</strong> Tambah lagi atau <a href="rangking.php">lihat semua data</a>.
</div>
<?php
    }

    else{
?>
<div class="alert alert-danger alert-dismissible" role="alert">
  <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
  <strong>Gagal Tambah Data!</strong> Terjadi kesalahan, coba lagi.
</div>
<?php
    }
    }
?>
<form method="post">
  <div class="form-group">
    <label for="ia">Alternatif</label>
    <select class="form-control" id="ia" name="ia">
        <?php
            $stmt3 = $pgn1->readAll();
            while ($row3 = $stmt3->fetch(PDO::FETCH_ASSOC)){
                extract($row3);
                echo "<option value='{$id_alternatif}'>{$nama_alternatif}</option>";
            }
        ?>
    </select>
  </div>
  <div class="form-group">
        <?php
            $stmt2 = $pgn2->readAll();
            while ($row2 = $stmt2->fetch(PDO::FETCH_ASSOC)){
                extract($row2);
        ?>
        <label for="ik"><?php echo $nama_kriteria; ?></label>
        <input type="hidden" name="ik[]" id="ik" value=<?php echo $id_kriteria ?>>
        <input type="text" class="form-control" id="nn" name="nn[]">
        <?php
            }
        ?>
  </div>
  <button type="submit" class="btn btn-primary">Simpan</button>
  <button type="button" onclick="location.href='rangking.php'" class="btn btn-success">Kembali</button>
</form>
<?php (print_r($_POST)); ?>

code of rangking.inc.php :

    function insert2(){

        $query = "insert into ".$this->table_name." values(?,?,?,'','')";
        $stmt = $this->conn->prepare($query);
        $stmt->bindParam(1, $this->ia);
        $stmt->bindParam(2, $this->ik);
        $stmt->bindParam(3, $this->nn);

        if($stmt->execute()){
            return true;
        }else{
            return false;
        }

    }

EDIT

mixing function code of _chris85_ and mine :

$query = "insert into ".$this->table_name." values(?,?,?,'','')";
foreach ($this->ik as $key => $value){
    $stmt = $this->conn->prepare($query);
    $stmt->bindParam(1, $this->ia);
    $stmt->bindParam(2, $value);
    $stmt->bindParam(3, $this->nn[$key]);
    if($stmt->execute()){
        return true;
    }else{
        return false;
    }
}

Answer 1

Since nn and ik are arrays you need to loop over them and bind each value. Here's a rough example of how you could do that assuming nn and ik have a one to one relationship.

$query = "insert into ".$this->table_name. " values";
error_log('IK' . print_r($this->ik, 1));
foreach($this->ik as $key => $value) {
     error_log('In Loop');
     $query_bits[] = '(?, ?, ?, "", "")';
     $params[] = $this->ia;
     $params[] = $value;
     $params[] = $this->nn[$key];
}
$stmt = $this->conn->prepare($query . implode(',' $query_bits));
$stmt->execute($params);

This is a rough, untested sample of how it should work.

Don't put variables into $query_bits or you will loose the purpose of preparing/binding.

This approach is making on large insert statement with each row's data separated by a comma.

INSERT statements that use VALUES syntax can insert multiple rows. To do this, include multiple lists of column values, each enclosed within parentheses and separated by commas.

- https://dev.mysql.com/doc/refman/5.7/en/insert.html