how to get value from select multiple on multiple rows ?

[pwfans]

php code to create multiple pages :

if ($input->post->submit) {
  $amount = count($input->post->field_1); 
  for($i=0;$i<$amount;$i++) {
    $p = new Page(); 
    $p->template = "template_1";  
    $p->parent = wire('pages')->get("/parent_1/");  
    $p->title = $input->post->field_1[$i];
    $p->name = $input->post->field_1[$i]; 
    foreach ($input->post->field_2 as $result) {
      $p->text.= $result." "; 
    }
    $p->save();
  }  
} 

html code :

<tr>
  <td><input type="text" name="field_1"></td>
  <td>
    <select name="field_2[]" multiple="multiple">
      <option value="opt_1">opt_1</option>
      <option value="opt_2">opt_2</option>
      <option value="opt_3">opt_3</option>
    </select>  
  </td>
</tr>

<tr>
  <td><input type="text" name="field_1"></td>
  <td>
    <select name="field_2[]" multiple="multiple">
      <option value="opt_1">opt_1</option>
      <option value="opt_2">opt_2</option>
      <option value="opt_3">opt_3</option>
    </select>  
  </td>
</tr>

... and another <tr>..</tr> addition using javascript 

There is off course incorrect value on field_2, they will contain same data get from field_2 on first row.
Have try on google search and not found any solution yet, there are talk about multi-dimensional array but still not understand how to implement that.