PHP uses bit-and-operator & bitwise OR operator ' | ' to implement rights management

This is the permission value.
2^0=1, the corresponding 2 in the number of "0001″ (here ^ I expressed as a" sub-party ", that is: 2 of 0 parties, the same below)
2^1=2, the corresponding 2-in number is "0010″
2^2=4, the corresponding 2-in number is "0100″
2^3=8, the corresponding 2-in number is "1000″

To judge a number within certain numbers, you can use the & operator (the value is derived from the table above)
such as: 7=4|2|1 (You can also easily understand into 7=4+2+1)
Use & to operate, you can know 7&4, 7&2, 7&1 are true, and if 7&8 is False

Example:
<?php
Define Permissions
Define ("Mhight", 16);//higher permissions, 2 4-time
Define ("Mdelete", 8);//delete permission, 2 of 3 times
Define ("Mupload", 4);//upload permissions, 2 2-time
Define ("Mwrite", 2);//write permission, 2 1-time
Define ("Mread", 1);//Read-only, 2 0-time

Assign a value to a permission
Echo Mdelete|mupload|mwrite|mread;

if (& 16)
Echo ' has higher authority <br> ';

Judge permissions with & "bits and characters", assuming permission value $key
$key = 13;//13=8+4+1
if ($key & Mdelete)
Echo ' has delete permission <br> ';

if ($key & Mupload)
Echo ' has upload permission <br> ';

if ($key & Mwrite)
Echo ' has write permission <br> ';

if ($key & Mread)
Echo ' has read-only access <br> ';

//////////////////////////////////////////////////////////////
$key = 13;//13=8+4+1
if ($key & 8)
Echo ' has delete permission <br> ';

if ($key & 4)
Echo ' has upload permission <br> ';

if ($key & 2)
Echo ' has write permission <br> ';

if ($key & 1)
Echo ' has read-only access <br> ';

?>

One of the algorithms for the privilege score is this, which can be said to be simple and efficient. I do not know that we understand no, do not understand it is OK, remember the example on the line. The premise is to do a good job of distributing the permission values, that is, the 1, 2, 4, 8, 16 ... (there is also a sequential problem, the more advanced the permission is the higher the permission value, such as the above example demonstrates the deletion of the permissions). With the Permission distribution table can determine to a person what permissions, you simply understand to which permission to add the corresponding permission value it.
This method is very useful, the disadvantage is that if the permissions are distributed fine, then the authority value will be more and more large, you think about it, 2 of several parties, if all the permissions are all added. But that's enough for general permission.