在我的多維數組的foreach循環中出現什麼錯誤？

Question

以下是我的多維數組命名$prev_map_data：

Array 
(
    [0] => Array 
     (
      [class_id] => 2 
      [class_name] => II 
      [class_checked] => 1 
      [class_subjects] => Array 
       (
        [0] => Array 
         (
          [cs_map_id] => 81 
          [subject_name] => 11 Engllish 
          [subject_checked] => 1 
          [teacher_cs_id] => 81 
         ) 

       ) 

     ) 

    [1] => Array 
     (
      [class_id] => 3 
      [class_name] => III 
      [class_checked] => 1 
      [class_subjects] => Array 
       (
        [0] => Array 
         (
          [cs_map_id] => 155 
          [subject_name] => Hidi 
          [subject_checked] => 1 
          [teacher_cs_id] => 155 
         ) 

        [1] => Array 
         (
          [cs_map_id] => 156 
          [subject_name] => 11 Maths 
          [subject_checked] => 1 
          [teacher_cs_id] => 156 
         ) 

        [2] => Array 
         (
          [cs_map_id] => 157 
          [subject_name] => 11 Science 
          [subject_checked] => 1 
          [teacher_cs_id] => 157 
         ) 

       ) 

     ) 

) 

我想一個擺脫關鍵[cs_map_id]一個所有的值和數組$data推值。但得到警告

Warning: Invalid argument supplied for foreach() 

我不明白我的代碼有什麼問題。任何人都可以幫助我改進我的代碼並將值附加到新數組中嗎？提前致謝。我的代碼如下：

$prev_map_data = $objTeacherClassesSubjects->GetClassSubjectMappingsbyTeacherId ($request, $teacher_class_subjects_error_messages); 
//print_d($prev_map_data); 
$data = array(); 
foreach($prev_map_data as $map_id){ 
    foreach($map_id as $ast){ 
     foreach($ast as $tp){ 
      //print_p($tp); 
      $tp['cs_map_id']; 
      array_push($data,$tp['cs_map_id']); 
     } 
    } 
} 

Answer 1

你無條件地挖掘到陣列上本身不是數組的項目。取而代之：

foreach($prev_map_data as $map_id){ 
    foreach($map_id['class_subjects'] as $subject){ 
     $data[] = $subject['cs_map_id']; 
    } 
} 

Answer 2

使用此

$arr = array(); 

foreach($prev_map_data as $map_id){ 
    $i = 0; 
    foreach($map_id['class_subjects'] as $val) { 

     $arr[$i] = $val['cs_map_id']; 
     $i++; 
    } 
}