PHP bitwise left shifting 32 spaces problem and bad results with large numbers arithmetic operations

Posted by Victor Stanciu on Stack Overflow See other posts from Stack Overflow or by Victor Stanciu
Published on 2010-03-17T11:48:30Z Indexed on 2010/03/17 11:51 UTC
Read the original article Hit count: 516

Filed under:

php

|

bitwise

|

precision

|

large

Hello,

I have the following problems:

First: I am trying to do a 32-spaces bitwise left shift on a large number, and for some reason the number is always returned as-is. For example:

echo(516103988<<32); // echoes 516103988

Because shifting the bits to the left one space is the equivalent of multiplying by 2, i tried multiplying the number by 2^32, and it works, it returns 2216649749795176448.

Second: I have to add 9379 to the number from the above point:

printf('%0.0f', 2216649749795176448 + 9379); // prints 2216649749795185920

Should print: 2216649749795185827

© Stack Overflow or respective owner

Related posts about php

Magento, NGINX, PHP-FPM, APC, MEMCACHED, 16gb Ram CentOS, Spiking PHP-FPM to 100% CPU

as seen on Server Fault - Search for 'Server Fault'
I have been trying to resolve my issue of spiking cpu caused by php-fpm processes. I've reduced the php-fpm config settings to: pm = ondemand pm.max_children = 12 pm.start_servers = 2 pm.min_spare_servers = 2 pm.max_spare_servers = 10 pm.max_requests = 500 php_admin_value[memory_limit] = 128M Problem… >>> More
PHP Pear Installation on CentOS

as seen on Server Fault - Search for 'Server Fault'
[root@ip ~]# yum install php-pear* Reducing CentOS-5 Testing to included packages only Finished Setting up Install Process Package 1:php-pear-1.8.1-2.el5.centos.noarch already installed and latest versio … >>> More
Apache configurations for php "AddType text/html php" or "AddType application/x-httpd-php php .php"

as seen on Server Fault - Search for 'Server Fault'
I am taking over an application server and discover that it contain the following settings: AddType text/html php Although it works, but my understanding is that it should set as following: AddType application/x-httpd-php php .php What are the key differences between the two settings?… >>> More
mod_rewrite settings causes server to throw HTTP 500 errors instead of 404

as seen on Server Fault - Search for 'Server Fault'
Hello. I have a server with VBulletin forum (working under Apache 2.2, CentOS). The default settings for it in .htaccess are as follows: RewriteEngine on RewriteCond %{HTTP_HOST} ^gsmforum\.ru RewriteRule (.*) http://www.gsmforum.ru/$1 [R=301,L] # If you are having problems or are using VirtualDocumentRoot… >>> More
Problems installing Memcache (PECL extension)

as seen on Server Fault - Search for 'Server Fault'
I have installed memcached fine, and now I will need to install PECL extension memcache. Im running RedHat x86_64 es5. The installation gives me this: downloading memcache-2.2.6.tgz ... Starting to download memcache-2.2.6.tgz (35,957 bytes) ..........done: 35,957 bytes 11 source files, building running:… >>> More

Related posts about bitwise

Bitwise AND, Bitwise Inclusive OR question, in Java

as seen on Stack Overflow - Search for 'Stack Overflow'
I've a few lines of code within a project, that I can't see the value of... buffer[i] = (currentByte & 0x7F) | (currentByte & 0x80); It reads the filebuffer from a file, stored as bytes, and then transfers then to buffer[i] as shown, but I can't understand what the overall purpose is, any… >>> More
What kind of specific projects can I do to master bitwise operations in C++? Also is there a canonical book? [closed]

as seen on Programmers - Search for 'Programmers'
I don't use C++ or bitwise operations at my current job but I'm thinking of applying to companies where it is a requirement to be fluent with them (on their tests anyway). So my question is: Can anyone suggest a project which will require gaining a fluency in bitwise operations to complete? On a… >>> More
Bit Reversal using bitwise

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all I am trying to do bit reversal in a byte. I use the code below static int BitReversal(int n) { int u0 = 0x55555555; // 01010101010101010101010101010101 int u1 = 0x33333333; // 00110011001100110011001100110011 int u2 = 0x0F0F0F0F; // 00001111000011110000111100001111 int u3… >>> More
Real world use cases of bitwise operators

as seen on Stack Overflow - Search for 'Stack Overflow'
What are some real world use cases of the following bitwise operators? AND XOR NOT OR >>> More
PHP bitwise left shifting 32 spaces problem and bad results with large numbers arithmetic operations

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, I have the following problems: First: I am trying to do a 32-spaces bitwise left shift on a large number, and for some reason the number is always returned as-is. For example: echo(516103988<<32); // echoes 516103988 Because shifting the bits to the left one space is the equivalent… >>> More