The problem is also affected on round().

<?php
$a=-0.1
echo round($a);
// results: -0
?>

Regards,

Steve

This is expected behavior. ceil() and floor() return a float because of the large range of supported numbers.

Derick

Bogus?

It is true that ceil() and round() return floating point numbers, but -0 is not a number.

Hi derick,

here is the proof of my statement.

try this code:

<?php
echo "<tt>(machine code representation)<br><br>";

// correct result
$b1=0;
$p=pack('f',$b1);
echo " $b1 = ";
for ($l=0,$o1='';$l<strlen($p);$l++){
	$o1.=sprintf('%02X',ord($p[$l]));
}
echo $o1.'h';
echo '<hr size=1>';

//wrong result
$a=-0.1;
$b2=round($a);
$p=pack('f',$b2);
echo "$b2 = ";
for ($l=0,$o2='';$l<strlen($p);$l++){
	$o2.=sprintf('%02X',ord($p[$l]));
}
echo $o2.'h';

echo "<hr>the question is, is $b1 == $b2<br>";
echo "php mean:<br><font color=#000088>";
if ($b1==$b2) echo "yes, this is true.<br>";
else echo "no, this is false.<br>";
echo "</font>but $o1 != $o2<br>";
echo "and also $o2 != 0";

echo "</tt>";
?>


The big problem with this behavior is, if you using round() or ceil() to output results
of mathematical function, you can't be sure if the result what you expected or not.

This can have fatal consequences for programs they output e.g. statitics in text files and
other programs interpret the php results wrong!

This is not a trivial problem!

The php functions just wrap calls to the underlining C library. On Linux glibc happens to return -0 on ceil. Very little we can do here.