Problem with Floats! (in PHP)

What's wrong with php floats?

$v = 5.2 * 3;

if($v==15.6) {
    echo 'Everything is fine =)';
} else {
    echo 'Okay something is wrong :S';
    var_dump($v); // float 15.6
}

Check this out too:

$v = 5.2 * 3;

if($v>15.6 AND $v<15.60000000001) {
    echo 'We are doomed :S';
    var_dump($v); // float 15.6
} else {
    echo 'Everything is fine =)';
}

I guess it has something to do with the internal representation or some obscure low level stuff? If that's the case, how do I get around this issue? Anything else I should know before using this to开发者_JS百科 calculate real money transactions?

I am sure this is a duplicate, so I'm making this a CW

$v = 5.2 * 3;
if (bccomp($v, 15.6) === 0) {
    echo 'Everything is fine =)';
} else {
    echo 'Okay something is wrong :S';
    var_dump($v); // float 15.6
}

will give 'Everything is fine =)'

It has to do with the internal representation indeed :). Never compare float values. I think there will exists php classes/modules that work around this problem, but you can also store your money values as integers and multiply them by 100. Before display you can divide them again :)

This has to do with floats in general and is not limited to PHP.

When using floats you should check for intervals with a specific precision, just as you did in your last example:

if(abs($v - 15.6) < 0.0001)
{
    // Yey :)
}

You can run into a lot of problems when using exact values.

the value you are getting is 15.600000000000001 and it is diferent to 15.6, this topic has been widely discussed, you can take a look to this threads:

• Imprecise numbers with microtime and floating point addition in PHP
• Compare floats in php

HTH, Regards

The PHP page on floats has a warning against comparing for equality and also links to this page which links to bccomp.

If you really need to compare floats check for being in bounds of an allowed deviation instead of an exact match, like

$DEVIATION = 0.0001;
if(abs($v-15.6)<$DEVIATION) ...

$v = 5.2 * 3;

if((string)$v == "15.6") {
    print "yes";
}

It's always good to check PHP website as most developers have come across problems before PHP.net Floating Point Number this comment shows a function for comparing floats.

<?php 
    function IsFloatEqual($x,$y,$precision=0.0000001) 
    { 
        return ($x+$precision >= $y) && ($x-$precision <= $y); 
    } 
?> 

Just a minor addition for anywone looking:

the BC* functions are the only true way to work with floats in PHP!