range(-8.00, 8.00, 0.05) acting very strange

Question

Does anyone know why range(-8.00, 8.00, 0.05) seems fail?

Array
(
[0] => -8
[1] => -7.95
[2] => -7.9
[3] => -7.85
[4] => -7.8
[5] => -7.75
         


        

Answer 1

That's a known problem, hopefully already fixed. See bug #54459.

Basically now instead of making consecutive floating point additions, the range function now increments an integer and multiplies it by the step.

Basically, you know have:

-8.00, -8.00 + 1 * 0.05, -8.00 + 2 * 0.05, ...

instead of

-8.00, -8.00 + 0.05, -8.00 + 0.05 + 0.05, ...

You can see this makes a difference:

$ php
<?php
for ($i = 0; $i < 9.99; $i += .1) {}
echo sprintf("%.17f", $i);
^D
9.99999999999998046

while:

$ php -r 'echo sprintf("%.17f", .1*100);'
10.00000000000000000

Answer 2

You may want to try a range between 800 and -800 with steps of 5 and then add in the decimal points / divide by 100 afterward.

Answer 3

That would be because floating point numbers are not precise and not all numbers can be represented exactly using floats.