PHP foreach traversal multidimensional array implementation Way _php tips

Introduced
Normally our foreach can print each key => value in a one-dimensional array sequentially, but if it is a multidimensional array, it needs to be cycled in a nested loop, or recursive implementation, but these methods are not flexible enough, because when the array is not determined to be a few dimensions, There is no never-ending loop of nesting, if recursive is a solution, but how do you do it if you just want to use a foreach loop?

Implementation Way One
using PHP itself with the iterator class Recursiveiteratoriterator

  $test _arr = Array (1,2,3,array (4, ' AA ' =>5,6,array (7, ' BB ' =>8), 9,10), 11,12); 
  $arrayiter = new Recursivearrayiterator ($test _arr);
  $iteriter = new Recursiveiteratoriterator ($arrayiter);
  Direct printing can be printed in a horizontal order
  . foreach ($iteriter as $key => $val) { 
    echo $key. ' => '. $val; 
  } 
  Results/
  * 
    0=>1
    1=>2 
    2=>3
    0=>4
    aa=>5
    2=>6 Bb=>8
    4=>9
    5=>10
    4=>11
    5=>12
 * *

Implementation Mode Two
Implement a recursiveiteratoriterator-like iterator class to realize multidimensional array horizontal printing function

Class Foreachprintfarr implements iterator {//current array scope private $_items;
    Private $_old_items; 

    Save every execution array environment stack private $_stack = array ();
    Public function __construct ($data =array ()) {$this->_items = $data;

      Private Function _isset () {$val = current ($this->_items);
      if (Empty ($this->_stack) &&! $val) {return false;
      else {return true;
      The public Function current () {$this->_old_items = null;

      $val = current ($this->_items);
        If it is an array, it saves the current execution environment and then switches to the new array execution Environment if (Is_array ($val)) {Array_push ($this->_stack, $this->_items);
        $this->_items = $val;
      return $this->current (); //Determine if the current execution needs to be cut back to the last execution Environment//(1) If there is a jump to continue execution/(2) if it does not exist and the environment stack is empty, the current execution to the last element//(3) If an element is not present in the current array environment
      In, save the current execution array environment $this->_old_items = $this->_items; Then switch the last execution environment $this->_items = Array_pop ($this->_stack) continue to loop, straightThe next//element is not empty until the current array environment while (1) {if (Next ($this->_items)) {prev ($this->_items); Bre
        Ak
        } elseif (Empty ($this->_stack)) {End ($this->_items);
          else {end ($this->_items);
          if (! $this->_old_items) $this->_old_items = $this->_items;
        $this->_items = Array_pop ($this->_stack);
    } return $val;  
    Public function Next () {Next ($this->_items); The Public Function key () {//Because the key () function executes after the current () function//So switches the execution environment in the current () function, which results in the previous execution environment before switching the last K EY//becomes the key after switching, so $this->_old_items Save the execution environment before or after the switch to prevent key printing error return $this->_old_items?
    Key ($this->_old_items): Key ($this->_items);
    The Public Function rewind () {Reset ($this->_items);
    The public function valid () {return $this->_isset ();

}
  } 

Internal execution mode

1, the Foreach Loop our custom Foreachprintfarr class, will automatically call the internal 5 methods valid (), rewind (), key (), next (), current () we only need to implement these several methods.

2, call Order:
1th time => Rewind-> valid-> current-> key
2nd time ~n => next-> valid-> current-> key

   $test _arr = Array (1,2,3,array (4, ' AA ' =>5,6,array (7, ' BB ' =>8), 9,10), 11,12);
   $iteriter = new Foreachprintfarr ($test _arr);
   foreach ($iteriter as $key => $val) {
     echo $key. ' => '. $val;
   } 
   Results:/
   * 
   0=>1
   1=>2
   2=>3
   0=>4
   aa=>5
   2=>6 Bb=>8
   4=>9
   5=>10
   4=>11
   5=>12
   * *

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