PHP迭代器和生成器用法实例分析

<?php
class Sample implements Iterator{
  private $curIndex=0;
  private $items=null;
  public function __construct($_items) {
    $this->items = $_items;
  }
  public function current (){
    echo "current\n";
    return $this->items[$this->curIndex];
  }
  public function key (){
    echo "key\n";
    return $this->curIndex;
  }
  public function next (){   
      echo "next\n"; 
      $this->curIndex++;
  }
  public function rewind (){
      $this->curIndex = 0;   
  }
  public function send ( $value ){
    if($value == "stop"){
      $this->curIndex = null;
    }
  }
  public function valid (){
    echo "valid\n";
    return isset($this->items[$this->curIndex]);
  }
}
$sample = new Sample([1,2,3]);
foreach ($sample as $k =>$v){
}

<?php
function gen_one_to_three() {
  for ($i = 1; $i <= 3; $i++) {
    //注意变量$i的值在不同的yield之间是保持传递的。
    yield $i;
  }
}
$generator = gen_one_to_three();
foreach ($generator as $value) {
  echo "$value\n";
}
var_dump($generator); //实际上是Generator对象

function myYeild(){
  $args = func_get_args();
  return new Sample($args);
}
$generator = myYeild(1,2,3);
foreach ($generator as $value) {
  echo "$value\n";
}

class AllUser implements \Iterator
{
  protected $index = 0;
  protected $data = [];
  public function __construct()
  {
    $link = mysqli_connect('192.168.0.91', 'root', '123', 'xxx');
    $rec = mysqli_query($link, 'select id from doc_admin');
    $this->data = mysqli_fetch_all($rec, MYSQLI_ASSOC);
  }
  //1 重置迭代器
  public function rewind()
  {
    $this->index = 0;
  }
  //2 验证迭代器是否有数据
  public function valid()
  {
    return $this->index < count($this->data);
  }
  //3 获取当前内容
  public function current()
  {
    $id = $this->data[$this->index];
    return User::find($id);
  }
  //4 移动key到下一个
  public function next()
  {
    return $this->index++;
  }
  //5 迭代器位置key
  public function key()
  {
    return $this->index;
  }
}
//实现迭代遍历用户表
$users = new AllUser();
//可实时修改
foreach ($users as $user){
  $user->add_time = time();
  $user->save();
}