PHP multiple value for loop

Question

I have the following php for loop

$screen = 1.3; // it can be other decimal value
    for ($i = 1, $k = 0; $i <= $screen; $i += 0.1, $k+=25) {
    echo $i . ' - ' . $k . '<br>';
}

It works fine but i would like to run the for loop til 1.3 - 75 now it print me 1.2 - 50. I try to change $i <= $screen to $i = $screen but it does not work.

Why use a decimal value for the loop though? – Daan Oct 20 '16 at 11:34 — Daan, Oct 20 '16 at 11:34
I haver to use decimal values its my task :/ – Zsolt Janes Oct 20 '16 at 11:38 — Zsolt Janes, Oct 20 '16 at 11:38
Kumar how do you mean this? – Zsolt Janes Oct 20 '16 at 11:40 — Zsolt Janes, Oct 20 '16 at 11:40
Welcome to floating point notation problems – apokryfos Oct 20 '16 at 11:42 — apokryfos, Oct 20 '16 at 11:42

score 5 · Accepted Answer · edited Jun 20 '20 at 09:12

If you read http://php.net/manual/en/language.types.float.php there's a nice statement you should keep in mind:

Testing floating point values for equality is problematic, due to the way that they are represented internally

To test floating point values for equality, an upper bound on the relative error due to rounding is used. This value is known as the machine epsilon, or unit roundoff, and is the smallest acceptable difference in calculations.

Based on the recommendation there you need to do something like :

<?php
$screen = 1.3; // it can be other decimal value
$epsilon=0.0001;
for ($i = 1, $k = 0; $i <= $screen+$epsilon; $i += 0.1, $k+=25) {
    echo $i . ' - ' . $k . "\n";
}

Thx for posting this answer even if there was one from me! And big thx for the refrence! Had a nearly similar problem some days ago, a bit mor complex and you just helped me to solve it. — Twinfriends, Oct 20 '16 at 13:49

score 2 · Answer 2 · answered Oct 20 '16 at 11:41

Two solutions:

$screen = 1.4; // it can be other decimal value
    for ($i = 1, $k = 0; $i <= $screen; $i += 0.1, $k+=25) {
    echo $i . ' - ' . $k . '<br>';
}

OR:

$screen = 1.3; // it can be other decimal value
    for ($i = 1, $k = 0; $i <= $screen+0.1; $i += 0.1, $k+=25) {
    echo $i . ' - ' . $k . '<br>';
}

Tested. Both work... as far i have understand what you want to do.

Tested Output of both:

1 - 0
1.1 - 25
1.2 - 50
1.3 - 75

score 0 · Answer 3 · edited May 23 '17 at 12:25

0

You got your answer, that's great another way to achieve the same is as follows. Source

$start = 1;
$end = 1.3;
$place = 1;

$step = 1 / pow(10, $place);

for($i = $start, $k=0; $i <= $end; $i = round($i + $step, $place), $k += 25)
{
    echo $i . ' - ' . $k . '<br>';
}

edited May 23 '17 at 12:25

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answered Oct 20 '16 at 11:47

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PHP multiple value for loop

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