PHP ArrayAccess 接口

在 PHP 中，ArrayAccess 接口用于开发一个类，该类提供对数组属性之一的类似数组的访问。可以在对象创建期间操作此类数组属性而不暴露它。 ArrayAccess接口定义了以下抽象方法

ArrayAccess {
   /* Methods */
   abstract public offsetExists ( mixed $offset ) : bool
   abstract public offsetGet ( mixed $offset ) : mixed
   abstract public offsetSet ( mixed $offset , mixed $value ) : void
   abstract public offsetUnset ( mixed $offset ) : void
}

ArrayAccess::offsetExists - 偏移量是否存在

ArrayAccess::offsetGet - 要检索的偏移量< /p>

ArrayAccess::offsetSet - 为指定的偏移量分配一个值

ArrayAccess::offsetUnset - 取消设置偏移量。

ArrayAccess::offsetUnset - 取消设置偏移量。 p>ArrayAccess 示例

在下面的示例中，关联数组是 myclass 的内部私有属性。键充当偏移量。我们可以设置、检索和取消设置数组中的项目。如果未给出偏移量，则会将其视为整数，每次递增到下一个索引。

 实时演示

<?php
class myclass implements ArrayAccess {
   private $arr = array();
   public function __construct() {
      $this->arr = array(
         "Mumbai" => "Maharashtra",
         "Hyderabad" => "A.P.",
         "Patna" => "Bihar",
      );
   }
   public function offsetSet($offset, $value) {
      if (is_null($offset)) {
         $this->arr[] = $value;
      } else {
         $this->arr[$offset] = $value;
      }
   }
   public function offsetExists($offset) {
      return isset($this->arr[$offset]);
   }
   public function offsetUnset($offset) {
      unset($this->arr[$offset]);
   }
   public function offsetGet($offset) {
      return isset($this->arr[$offset]) ? $this->arr[$offset] : null;
   }
}
$obj = new myclass();
var_dump(isset($obj["Mumbai"]));
var_dump($obj["Mumbai"]);
unset($obj["Mumbai"]);
var_dump(isset($obj["Mumbai"]));
$obj["Bombay"] = "Maharashtra";
var_dump($obj["Bombay"]);
$obj["Chennai"] = 'Tamilnadu';
$obj[] = 'New State';
$obj["Hyderabad"] = 'Telangana';
print_r($obj);
?>

上述程序显示以下输出

bool(true)
string(11) "Maharashtra"
bool(false)
string(11) "Maharashtra"
myclass Object(
   [arr:myclass:private] => Array(
      [Hyderabad] => Telangana
      [Patna] => Bihar
      [Bombay] => Maharashtra
      [Chennai] => Tamilnadu
      [0] => New State
   )

)

类的数组属性也可以是索引数组。在这种情况下，元素的索引（从 0 开始）充当偏移量。当调用不带 offset 参数的 offsetSet(0 方法时，数组索引将递增到下一个可用整数

<?php
class myclass implements ArrayAccess {
   private $arr = array();
   public function __construct() {
      $this->arr = array("Mumbai", "Hyderabad", "Patna");
   }
   public function offsetSet($offset, $value) {
      if (is_null($offset)) {
         $this->arr[] = $value;
      } else {
         $this->arr[$offset] = $value;
      }
   }
   public function offsetExists($offset) {
      eturn isset($this->arr[$offset]);
   }
   public function offsetUnset($offset) {
      unset($this->arr[$offset]);
   }
   public function offsetGet($offset) {
      return isset($this->arr[$offset]) ? $this->arr[$offset] : null;
   }
}
$obj = new myclass();
var_dump(isset($obj[0]));
var_dump($obj[0]);
unset($obj[0]);
var_dump(isset($obj[0]));
$obj[3] = "Pune";
var_dump($obj[3]);
$obj[4] = 'Chennai';
$obj[] = 'NewDelhi';
$obj[2] = 'Benguluru';
print_r($obj);
?>

上述程序显示以下输出

bool(true)
string(6) "Mumbai"
bool(false)
string(4) "Pune"
myclass Object(
   [arr:myclass:private] => Array(
      [1] => Hyderabad
      [2] => Benguluru
      [3] => Pune
      [4] => Chennai
      [5] => NewDelhi
   )

)