negative number

[Anon]

The coding is:
<?
$a=-2000000000;
$b=$a4;
$c=$a1;
echo -11474836489*1;
echo "<br>".$b;
echo "<br>".$c;
?>
The result will show:
-11474836489
589934592
-2000000000

Why a negative number multiply by a positive number is positive number?

It is strange that -1147483648>1000000000 is true?

[sridhar]

Try this:

<?
$a=-2000000000e0;
$b=$a4;
$c=$a1;
echo -11474836489*1;
echo "<br>".$b;
echo "<br>".$c;
?>

Prints out:
-11474836489
-8000000000
-2000000000

Remember, all numerical values are treated as int, so if you have a digit > (2³¹ - 1) or < -(2^31), then suffix it with e0 which will automatically make the literal a floating-point value.

BTW: When I do:
if(-1147483648e0>1000000000)

I get false. So I guess floating points have to be suffixed with a decimal or in scientific notation. I agree with you: It IS strange when you do just: -1147483648>1000000000 and it is true :-)

I think this is dumb. PHP should be like JavaScript and automatically decide data types for numerical values. The only thing I DONT like about JavaScript is that it treats ALL numerical values as floating points, which if done in PHP, memory allocation might be something to worry about. So I don't mind the way it is now in PHP, but I think in the future it should be modified so that if you DO declare a literal greater than the length allowed by the data-type, it should declare the variable with the next larger data type.
Does anyone else agree with me on this?

hope this helps,
-sridhar

[brandonschnell]

nope, its normal. by default php uses variables of type int. An int (4 bytes on most platforms) can hold about +/- 2 billion values. anything outside of that "wraps around" as the high bit which is used for the sign "flips".

try to typecast the variable:
$a=(double)-2000000000;

http://www.php.net/manual/en/language.types.type-juggling.php#language.types.typecasting