Description:
------------
It looks like overflow when I do plus 1. But when I do tims 2, it looks correct. Strange! I guess times and division move left or right for binery number(...1011101...). Plus and minus functions maybe have bugs? I don't know my code is wrong or it is a bug.

Server is Centos 5.3+PHP 5.2.11+Apache = Web Server
I just put this code into public_html

And client is WinXP+SP3+IE7. IE open the php. Wrong result.

Thanks a lot.

Reproduce code:
---------------
<?php
$x=2;
$p=100;
$y=pow($x,$p);
$a=number_format($y);
$b=$y+2;
$c=$y*2;
$r=number_format($a);
$rr=number_format($b);
echo "pow($x,$p)   = $a <br><br>";
echo "pow($x,$p)+2 = $r <br><br>";
echo "pow($x,$p)*2 = $rr <br><br>";
?>

Expected result:
----------------
pow(2,100)   = 1,267,650,600,228,229,401,496,703,205,376 

pow(2,100)+2 = 1,267,650,600,228,229,401,496,703,205,378 

pow(2,100)*2 = 2,535,301,200,456,458,802,993,406,410,752 


Actual result:
--------------
pow(2,100)   = 1,267,650,600,228,229,401,496,703,205,376 

pow(2,100)+2 = 1,267,650,600,228,229,401,496,703,205,376 

pow(2,100)*2 = 2,535,301,200,456,458,802,993,406,410,752