$sql = "UPDATE `MPP_PhoneSpec` 
     SET `idx`=?,
      `Availability`=?,
      `Battery`=?,
      `CPU`=?,
      `Camera`=?,
      `Casing`=?,
      `Connectivity-Data`=?,
      `Display`=?,
      `General`=?,
      `Memory`=?,
      `Operating-System`=?,
      `Other-Features`=?,
      `Size-Weight`=?
    WHERE `idx`=?";
 $stmt = $mysqli->prepare($sql);

 foreach ($_POST as $key=>$item){
  $stmt->bind_param('dssssssssssssd', 
        (int)$key, $item['Availability'],
        $item['Battery'], $item['CPU'],
        $item['Camera'], $item['Casing'],
        $item['Connectivity_Data'],
        $item['Display'], $item['General'],
        $item['Memory'], $item['Operating_System'],
        $item['Other_Features'], $item['Size_Weight'],(int)$key);
 }
 $stmt->execute();
 if ($stmt->errno) { echo "FAILURE!!! " . $stmt->error(); }
 else { echo "Updated {$stmt->affected_rows} rows"; }
 $stmt->close();
 $mysqli->close();