使用未知数字进行Round Down

Question

I have a table with a decimal field, which I need to round down.

Here's a data snippet of the table:

number
9.5
9.53
7.25
6.9
9.6
8.0
8.3
8.75
9.0
12.25
12.65
11.0

If a number is between XXX.0 and XXX.5 the number needs to round down to XXX.0 (eg. 8.3 or 12.25 expecting 8.0 or 12.0)

If the number is between XXX.5 and XXX.0 the number needs to round down to XXX.5 (eg. 9.53 or 9.6 expecting 9.5 or 9.5)

Else the number should stay unchanged (eg. 8.0 or 11.0)

Here is my question: How can I define what is in front of the decimal, this can be anything between 0 and 20? I have not found anything similar anywhere... Is there a way to only look at the value after the decimal?

Here is a sample code snipped, where XXX is the unknown part of the decimal number:

if(($number > XXX.0) && ($number < XXX.5))
    { $newNumber = round($number, 0, PHP_ROUND_HALF_DOWN); }

elseif(($number > XXX.5) && ($number < XXX.0))
    { $newNumber = round($number, 0, PHP_ROUND_HALF_DOWN); }

elseif(($number == XXX.5) || ($number == XXX.0))
    { $newNumber = $number; }

Answer 1

You can use fmod to return the floating point remainder, then do a simple ternary to output your desired result.

<?php

$n = array(
8.3, //8.0
12.25, //12.00
9.53, //9.5
9.6 //9.5
);

foreach($n as $i) {
   echo $i .' = '. (fmod($i, 1) > 0.5 
           ? sprintf("%2.f", (float) (int) $i + 0.5) 
           : sprintf("%2.f", (float) (int) $i)) . PHP_EOL; 
}

https://eval.in/411076

And in function form;

function round_mid($i) {
   return (fmod($i, 1) > 0.5 
             ? sprintf("%2.f", (float) (int) $i + 0.5) 
             : sprintf("%2.f", (float) (int) $i));
}

https://eval.in/411080