混淆php中的多维数组与foreach获取错误

Question

what is use of multidimensional array(2D,3D or what is the limit in multidimensional array) and foreach()? foreach() is use for printing values inside array? In case of multidimensional array why nested loop is important?

Errors:

Notice: Array to string conversion in C:\\xampp\\htdocs\\example\\basic\\foreach2.php on line 9 Arrayarray(3) { [0]=> int(4) [1]=> int(5) [2]=> int(7) }

Notice: Array to string conversion in C:\\xampp\\htdocs\\example\\basic\\foreach2.php on line 11

$items = array(1,2,3,
      array(4,5,7
     ),
     8,54,4,5,5);
foreach($items as $key => $value)
{
   echo $value;
   var_dump($value);
   echo $key ."pair match".$value . "<br>";
}

HOW do I access this array?

      $a_services = array(
        'user-login' => array(
          'operations' => array(
            'retrieve' => array(
              'help' => 'Retrieves a user',
              'callback' => 'android',
              'file' => array('type' => 'inc', 'module' => 'android_services'),
              'access callback' => 'services',
              'args' => array(
                array(
                  'name' => 'phone_no',
                  'type' => 'string',
                  'description' => 'The uid ',
                  'source' => array('path' => 0),
                  'optional' => FALSE,
                ),
              ),
            ),
          ),
         ),
        );
  print_r($a_services['$android_services ']['user-login']['operations']['retrieve']['callback']);
 print_r($a_services['$android_services ']['user-login']['operations']['retrieve']['callback']['args']['name']);

Error 1. Notice: Array to string conversion 2. Undefined index: $android_services 3. How to print with help of foreach 4. above array is 4 dimensional??????

Answer 1

To loop through this kind of array you need some sort of recursiveness.

I usually call a function inside the for each. the function tests whether the current element is an array. If so the functions call itself. If not the function does whatever (echo the value in your example).

Something like:

foreach($a_services as $key => $value) {
    do_your_thing($value);
}

function do_your_thing($recvalue)
{
    if (is_array($recvalue))
    {
        foreach($recvalue as $key => $value) 
        {
            do_your_thing($value);
        }
    }
    else
    {
        echo $recvalue;
    }
    return $recvalue;   
}

Answer 2

You can define multidimension arrays (arrays including oher arrays) in PHP.

For example you have 2 different lists, one for grocery shopping, one for daily task.

$lists = array(
    'grocery' => array('banana', 'apple'),
    'tasks' => array('go to work', 'wash dishes'),
);

If you want to check all levels of arrays, you should use nested loops. For example you can use foreach , it will iterate over arrays first level.

foreach($lists as $list)
    return $list; // returns grocery[] and tasks[]

As you see this loop returning other loop. So if you need to list all grocery[] array items, you need iterate again in this array.

foreach($lists as $list)
    foreach($list as $k => $l)
        if($k == 'grocery')
            echo $l; // echos "banana","apple"

Nested loops are important (and necessary) to reach multidimensional arrays contents especially if you don't know structure of the array. These loops will find all array items for you. But if you know structure, you can directly use $lists['grocery'] to reach grocery array or $lists['grocery'][0] to reach first element of your grocery list.