Unreliable php exclusive or operations

However, it seems that there is a problem on the server, and it is always impossible to get it, but there is no problem with local debugging. the allow_url_fopen of php is on, and the file function test is successful, which is strange, you have time to proceed. Written yesterday


However, it seems that there is a problem on the server, and it is always impossible to get it, but there is no problem with local debugging. the allow_url_fopen of php is on, and the file function test is successful, which is strange, you have time to proceed.


After work today, I will study this again. during the careful analysis of the pr. php file, I found that the final focus problem lies in
$ A ^ = (zeroFill ($ c, 13 ).
<? Php
$ A =-3862272608;
$ B = 471468;
$ C = $ a ^ $ B;
Echo $ c;


Echo'
This is a 5.2 php Windows XP system. The value of $ c is 432886796 ';
Echo'
The value of $ c for the 4.4 php and CentOs system on the server is-2147012180 ';
?>


Based on the above code, you can test it by yourself. The results of linux and windows are different.
It makes me very depressed. echo get_1__var ('Precision '); the accuracy of this query is the same.


Then Baidu found the following excerpt from the cu post:


Said the landlord


For the same code, php in linux and windows is different or the result is different. why?
The code is
<?
$ A =-5547163286;
$ B = 173240;
$ A ^ = $ B;
Echo $;
?>
In linux, the result is-2147310408.
In windows, the result is-1252022830.


What's going on? Have you ever met?




Second floor
This should not be a system problem. it should be a machine problem.


Third floor
After following up, the message is sent out.
The value range of an integer in php is 2147483647 ~ -2147483647
Therefore, the above value $ a is theoretically overflow.
But the strange thing is that, after the value is assigned, echo $ a again, and the overflowed value is printed.
Why?
I cannot touch the North ......


Fourth floor
The length of the integer is related to the platform, although the maximum value is usually about 2 billion (32-bit signed ). PHP does not support unsigned integers.


Fifth Floor
To: HonestQiao
Moderator, Hello, the platform is related to the operating system, right?
How can I execute
$ A =-5547163286;
$ B = $;
The result of echo $ B; is-5547163286;
Since it overflows, $ B should not be the original value after the value is assigned.


6th Floor
Check whether this problem can be solved.


7th Floor
Http://cn.php.net/manual/zh/language.types.integer.php
Combination:
Http://cn.php.net/manual/zh/language.types.type-juggling.php
Take a look:
You can test separately:
$ A =-5547163286;
Printf ("% s \ n", gettype ($ ));
$ B = $;
Printf ("% s \ n", gettype ($ B ));
$ A =-5547163286;
Printf ("% s \ n", gettype ($ ));
$ B = 173240;
Printf ("% s \ n", gettype ($ B ));
$ A ^ = $ B;
Printf ("% s \ n", gettype ($ ));
Echo $;


Eighth Floor
According to the prompts in HonestQiao, the test results are as follows:
Test 1:
<?
$ A =-5547163286;
Printf ("% s \ n", gettype ($ ));
$ B = 173240;
Printf ("% s \ n", gettype ($ B ));
$ A ^ = $ B;
Printf ("% s \ n", gettype ($ ));
Echo $;
?>
Result: double integer-2147310408
Test 2:
<?
$ A =-5547163286;
Printf ("% s \ n", gettype ($ ));
$ B = (double) 173240;
Printf ("% s \ n", gettype ($ B ));
$ A ^ = $ B;
Printf ("% s \ n", gettype ($ ));
Echo $;
?>
Result: double integer-2147310408
Test 3:
<?
$ A =-5547163286;
Printf ("% s \ n", gettype ($ ));
$ B = (double) 173240;
Printf ("% s \ n", gettype ($ B ));
$ A = (double) ($ a ^ $ B );
Printf ("% s \ n", gettype ($ ));
Echo $;
?>
Result: double-2147310408


The calculation result is-2147310408, which is an incorrect value.
I now basically think that the large numbers of php in linux may be different or exceptions or errors may occur.
What do you think?




9th floor
I mean, it will convert the data type.
At the same time, when the range is exceeded, the behavior is unpredictable.
Then I ran back to a post.
So far. It can be determined that the reason is the server.
The value range of an integer in php is 2147483647 ~ -2147483647
In linux, php integer overflow results are unreliable.
That is to say, this pr query can only be used on windows servers .......