how to compare 2 numbers?

Hi,

The server I use is running PHP 4 and PHP 5. I have run the following codes and don't understand why none of the if statement return true since the results should be 58 no matter what. What is the best way to compare 2 numbers regardless how many decimal points they have.

<?php
$a= .58;
$b= 100;
$c = 58.0000;

if (($a * $b) == $c)
{
print 'a*b == c';
print '$a'.$a.' '; print '$b'.$b.' '; print '$c'.$c.' ';
}
else
{
print 'duh1? if (($a * $b) == $c)<br />';
print '$a '.$a;
print '<br />';
print '$b '.$b;
print '<br />';
print '$c '.$c;
print '<br />';
print '<br />';
}

if (($a * $b) == (int)$c)
print 'a*b == c';
else{
print 'duh2? if (($a * $b) == (int)$c)';
print '<br />';
print '($a * $b) '.$a * $b;print '<br />';
print '(int)$c '.(int)$c;print '<br />';
print '<br />';
}

if (((int)($a * $b)) == (int)$c)
{print 'a*b == c';
print (int)($a * $b);
}
else
{
print 'duh3? if (((int)($a * $b)) == (int)$c)';
print '<br />';
print '(int)($a * $b) '.(int)($a * $b); // this one return 57 instead the expecting 58
print '<br />';
print '(int)$c '.(int)$c;print '<br />';
print '<br />';
}
if (($a * $b) == ($c * 1))
print 'a*b == c';
else
{
print 'duh4? if (($a * $b) == ($c * 1))';print '<br />';
print '($a * $b) '.($a * $b);print '<br />';
print '($c * 1) '.($c * 1);print '<br />';
}

?>

 

You should never compare floating point numbers, it says so right in the PHP manual. You may get your desired result like this, but it's still not recommended:

$y = intval(round(($a * $b), 2));
$c = intval(round($c, 2));

if ($y == $c) { }

PHP:

 

Thank you very much, steelaz.

You gave me an idea. I will use floatval() to do the comparison. This will work for me.

Thanks again.

 

I tried the above code but i have some questions related to it.

1. Why PHP is so general in numbers syste although C or C++ is not. We must declare int, float or any other data type ..
2. How can i control compiler of the wamp ..??


Regards