为什么要在PHP中使用按位/掩码? [英] Why should I use bitwise/bitmask in PHP?
问题描述
我工作的用户角色/许可系统上的PHP脚本。
下面是一个使用位掩码方法,我发现在phpbuilder.com权限的code。
下面的部分是一个简单得多的版本w3hich可以做basicly同样的事情,没有小角色。
很多人都使用位运算符和等为PHP设置和其他东西推荐的,我永远无法理解为什么虽然。在code以下是有使用第一code而不是第二的任何益处
< PHP
/ **
*修正存储在阵列中的变量。
* @参数$整数位掩码整数
* @返回数组
* /
功能位掩码($面膜= 0){
$收益率=阵列();
而($面具大于0){
为($ i = 0,$ N = 0; $ I< = $面具; $ I = 1 * POW(2,$ N),$ N ++){
$结束= $ I;
}
$返回[] = $结束;
$面膜= $面具 - $结束;
}
排序($返程);
返回$返回;
}
定义('PERMISSION_DENIED',0);
定义('PERMISSION_READ',1);
定义('PERMISSION_ADD',2);
定义('PERMISSION_UPDATE',4);
定义('PERMISSION_DELETE',8);//运行功能
//这个值会从用户的设置MySQL表拉
$ _ARR_permission =掩码('5');如果(in_array(PERMISSION_READ,$ _ARR_permission)){
回声访问理所当然的。;
}其他{
回声访问被拒绝。;
}
?>
非位版本的
< PHP
/ *
非按位法
* ///这个值会从用户的设置MySQL表拉
$ user_permission_level = 4;如果($ user_permission_level === 4){
回声访问理所当然的。;
}其他{
回声访问被拒绝。;
}?>
为什么不这样做?
定义('PERMISSION_DENIED',0);
定义('PERMISSION_READ',1);
定义('PERMISSION_ADD',2);
定义('PERMISSION_UPDATE',4);
定义('PERMISSION_DELETE',8);//运行功能
//这个值会从用户的设置MySQL表拉
$ _ARR_permission = 5;如果($ _ ARR_permission&安培; PERMISSION_READ){
回声访问理所当然的。;
}其他{
回声访问被拒绝。;
}
您还可以创建很多,如果你使用的位...
权限任意组合 $ READ_ONLY = PERMISSION_READ;
$ read_delete = PERMISSION_READ | PERMISSION_DELETE;
$ full_rights = PERMISSION_DENIED | PERMISSION_READ | PERMISSION_ADD | PERMISSION_UPDATE | PERMISSION_DELETE;//操作权限是很容易...
$ myrights = PERMISSION_READ;
$ myrights | = PERMISSION_UPDATE; //添加更新允许我的权利
I am working on a user-role / permission system in PHP for a script.
Below is a code using a bitmask method for permissions that I found on phpbuilder.com.
Below that part is a much simpler version w3hich could do basicly the same thing without the bit part.
Many people have recommended using bit operators and such for settings and other things in PHP, I have never understood why though. In the code below is there ANY benefit from using the first code instead of the second?
<?php
/**
* Correct the variables stored in array.
* @param integer $mask Integer of the bit
* @return array
*/
function bitMask($mask = 0) {
$return = array();
while ($mask > 0) {
for($i = 0, $n = 0; $i <= $mask; $i = 1 * pow(2, $n), $n++) {
$end = $i;
}
$return[] = $end;
$mask = $mask - $end;
}
sort($return);
return $return;
}
define('PERMISSION_DENIED', 0);
define('PERMISSION_READ', 1);
define('PERMISSION_ADD', 2);
define('PERMISSION_UPDATE', 4);
define('PERMISSION_DELETE', 8);
//run function
// this value would be pulled from a user's setting mysql table
$_ARR_permission = bitMask('5');
if(in_array(PERMISSION_READ, $_ARR_permission)) {
echo 'Access granted.';
}else {
echo 'Access denied.';
}
?>
non-bit version
<?PHP
/*
NON bitwise method
*/
// this value would be pulled from a user's setting mysql table
$user_permission_level = 4;
if($user_permission_level === 4) {
echo 'Access granted.';
}else {
echo 'Access denied.';
}
?>
Why not just do this...
define('PERMISSION_DENIED', 0);
define('PERMISSION_READ', 1);
define('PERMISSION_ADD', 2);
define('PERMISSION_UPDATE', 4);
define('PERMISSION_DELETE', 8);
//run function
// this value would be pulled from a user's setting mysql table
$_ARR_permission = 5;
if($_ARR_permission & PERMISSION_READ) {
echo 'Access granted.';
}else {
echo 'Access denied.';
}
You can also create lots of arbitrary combinations of permissions if you use bits...
$read_only = PERMISSION_READ;
$read_delete = PERMISSION_READ | PERMISSION_DELETE;
$full_rights = PERMISSION_DENIED | PERMISSION_READ | PERMISSION_ADD | PERMISSION_UPDATE | PERMISSION_DELETE;
//manipulating permissions is easy...
$myrights = PERMISSION_READ;
$myrights |= PERMISSION_UPDATE; // add Update permission to my rights
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