Friday, February 23, 2018

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

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 are not documented, so reading the manual was not really helpful in this case.

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