Floating Point Comparisons In PHP and Javascript

By Justin Laing
2008-01-08

PHP Floating Point Comparison Made Easy

Here’s my php function that compares floating point numbers:

function moneycomp($a,$comp,$b,$decimals=2) {
	$res = bccomp($a,$b,$decimals); // php function for comparing floating point numbers with a specified level of precision
	switch ($comp) {
		case ">":
			return ($res==1);
		case ">=":
			return ($res==1 || $res==0);
		case "<":
			return ($res==-1);
		case "<=":
			return ($res==-1 || $res==0);
		default:
		case "==":
			return ($res==0);
	}
}

// example usage: if ($total > $payments) ...
if (moneycomp($total,'>',$payments)) ...

// example usage: if ($debt <= $income) ...
if (moneycomp($debt,'<=',$income) ...

// example usage: if ($cost == $price) ...
if (moneycomp($cost,'==',$price) ...

So that makes life really simple. You just write your comparisons wrapped in the moneycomp() function.

Tutorial Pages:
» Beware Comparing Floating Point Values Can Be Hazardous!
» PHP Floating Point Comparison Made Easy
» Javascript Floating Point Comparison Made Easy
» Resources And Further Reading

Originally posted on Makebeta

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