Question

How can the below be possible:

$varnum = 4;
if( $varnum/4 - floor($varnum/4) !== 0){
    echo 'foo';
}

This echoes ‘foo’ on my server running PHP 5.1.6. If i change the operator to == I get the same results.

I have no idea why, but could it possibly be because “==” is “equals” and “!==” is “Not identical”? How then would I make them identical? I guess in javaScript I would “parseInt”, but there is no such thing in PHP, right?

Answer 1

The reason this fails is because in PHP, the floor function returns a float, despite the fact that the value is always a whole number. You can see this in the documentation here: http://php.net/manual/en/function.floor.php

You’re doing a fixed type comparison of that float to an integer zero, so the result is false, regardless of whether the value is actually zero.

To fix this, either:

• cast the output of floor to an integer – either intval(float(...)) or (int)float(..)
• use != instead of !==.
• use 0.0 instead of just 0 to compare against.

In case you’re wondering why floor() would return a float rather than an integer, it’s because the input is a float. The float data type has a larger possible range than integer, and thus it is possible to call floor() on a value that would be too big to hold in an integer. Therefore it would not be safe for the function to return an integer; it returns a float instead so that it can guarantee the result will be correct.

It may seem odd at first glance, but hopefully that explains the logic behind it for you.