Type-juggling and (strict) greater/lesser-than comparisons in PHP?

Question

PHP is famous for its type-juggling. I must admit it puzzles me, and I'm having a hard time to find out basic logical/fundamental things in comparisons. For example: If `$a > $b` is true and `$b > $c` is true, must it mean that `$a > $c` is *always* true too? Following basic logic, I would say *yes* however I'm that puzzled I do not really trust PHP in this. Maybe someone can provide an example where this is not the case? Also I'm wondering with the strict lesser-than and strict greater-than operators (as their meaning is described as strictly which I only knew in the past from the equality comparisons) if it makes any difference if left and right operands are swapped with strictly unequal values: # Precondition: if ($a === $b) { throw new Exception( 'Both are strictly equal - can not compare strictly for greater or smaller' ); } ($a > $b) !== ($b > $a) For most of all type comparison combinations these [greater / lesser comparison operators](http://php.net/language.operators.comparison) are not documented, so reading the manual was not really helpful in this case.

Answer 1

PHP, similar to JavaScript, has evolved to a somewhat optional strictness of types.

What you describe could theoretically become a concern. Lets say $a is a float, resulting from a former operation/calculation. And $b is an integer.

Now, based on the precision problem, $b could in theory result in having a slightly different value than mathematically accurate.

As comparison operators themselves are strict, this could result in e.g. $b > $a being true while $b == $a false even though the values are the same from a mathematical perspective. This goes as far as

$a = 2.5;

$b = 1.5;

$bool = $b == ($a - 1);

In this case $bool is false, even though you expect it to be true. The solution is to round your values accordingly. You will find references to epsilon as a method of fighting this, but don't forget that complex mathematical operations could go through many calculations before you can determine the "offset".

$a = 2.5;

$b = 1.5;

$bool = round($b, 1) == round($a - 1, 1);

About your example:

($a > $b) !== ($b > $a)

So what are the possible outcomes here?

1. both expressions are true: the overall result is false
2. one expression is false, the other true: the overall result is true
3. both expressions are false: the overall result is false

So since you excluded that they are equal in your example, I can't think of any scenario that wouldn't securely hit the second possibility, regardless of type of number(s)