什么是& & 2在PHP中意味着什么? [英] What does & in &2 mean in PHP?

问题描述

在以下代码的最后一行中，它具有&2, if($page['special']&2).

In the last line of the following code, it has &2, if($page['special']&2).

&是什么是什么意思?

What does & mean?

if(isset($_REQUEST['id']))$id=(int)$_REQUEST['id'];
else $id=0;
if($id){ // check that page exists
    $page=dbRow("SELECT * FROM pages WHERE id=$id");
    if($page!==false){
        $page_vars=json_decode($page['vars'],true);
        $edit=true;
    }
}
if(!isset($edit)){
    $parent=isset($_REQUEST['parent'])?(int)$_REQUEST['parent']:0;
    $special=0;
    if(isset($_REQUEST['hidden']))$special+=2;
    $page=array('parent'=>$parent,'type'=>'0','body'=>'','name'=>'','title'=>'','ord'=>0,'description'=>'','id'=>0,'keywords'=>'','special'=>$special,'template'=>'');
    $page_vars=array();
    $id=0;
    $edit=false;
}

// { if page is hidden from navigation, show a message saying that
if($page['special']&2)echo '<em>NOTE: this page is currently hidden from the front-end navigation. Use the "Advanced Options" to un-hide it.</em>';

推荐答案

$page['special'] & 2

表示

$page['special'] 按位与 2

基本上检查是否在$page['special']中设置了2位.

It basically checks to see if the 2 bit is set in $page['special'].

此行:

if(isset($_REQUEST['hidden']))$special+=2;

明确地将$special加2，以便满足按位AND运算和比较，因为十进制2 ==二进制10，其中1代表2 ¹ 位，确保它是设置.

explicitly adds 2 to $special so that it'll satisfy the bitwise AND operation and comparison, because decimal 2 == binary 10, with the 1 representing the 2¹ bit, ensuring it is set.

如果设置了2位，则AND操作返回2，在PHP中解析为true并且满足条件；否则返回0，该值被视为false.

The AND operation returns 2 if the 2 bit is set, which resolves to true in PHP and satisfies the condition; otherwise it returns 0 which is considered false.

IMO相当巧妙，虽然不确定它的安全性.

Quite a neat trick IMO, not sure how secure it is though.

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