在PHP中舍入到最接近的5或9

Question

I need to round pricing of products to nearest 5 or 9 with a PHP function.

For example, it must always round up:

$243 would round up to $245

$247 would round up to $249

Currently using the following code, but this only rounds to nearest 5:

function round_five($num) {
    return round($num*2,-1)/2;
}

Any advice would be greatly appreciated <3

Answer 1

By checking whether the remainder of division by 10 is less than 5, we round it to 5, otherwise if it is greater than 5, we round it to 9. If not, the remainder is 5, and we return the number itself.

function my_round($number) {
    $inumber = ceil($number);

    $mod_10 = $inumber % 10;
    $mod_5 = $inumber % 5;

    if ($mod_10 < 5) {
        return $inumber + 5 - $mod_5;
    }

    if ($mod_10 > 5) {
        return $inumber + 10 - $mod_10 - 1;
    }

    return $inumber;
}

echo my_round(243) . PHP_EOL;
echo my_round(247) . PHP_EOL;
echo my_round(5) . PHP_EOL;
echo my_round(9) . PHP_EOL;
echo my_round(10) . PHP_EOL;
echo my_round(0) . PHP_EOL;
echo my_round(5.1) . PHP_EOL;
echo my_round(8.9) . PHP_EOL;
echo my_round(9.1) . PHP_EOL;

Outputs:

245
249
5
9
15
5
9
9
15

Requirements are a little vague, so it may still be tweaked to handle various other corner cases.

Answer 2

This is a bit, non mathy but should work:

function round9($n) {
    $n = ceil($n);
    $r = substr($n,-1) > 5 ? 9 : 5;
    $n = substr($n,0,-1) . $r;
    return $n;
}

• first round up to nearest integer
• get last digit
• replace last digit with 9 if it's greater than 5. otherwise replace with a 5.

UPDATE: I thought this was an interesting problem and now that we've got three correct answers which solve it from very different angles I thought I'd do a bit of performance analysis for my own curiosity. neuro_sys's answer wins by far! Here are the results in seconds to complete 10 million iterations:

time to build array: 1.7170281410217
round9: 10.753921985626
my_round: 1.6339750289917
rounder: 16.578145980835

Test was run on an 8GB, 4 Core Linode VPS running Ubuntu 16.04 / PHP 7.0.14

Answer 3

Related questions you should have read:

• Round up to nearest multiple of five in PHP

This is the solution:

Because your issue is not using core mathemtics (5 and 9 are arbitary) or large indicies (largest count is 5 digits, 0,1,2,3,4) , simply count the numbers up:

<?php
function rounder($n) {
    $x=[5,9];
    $zz = ceil($n);
     $b = substr((string)$zz, -1); 
    while( !in_array($b,$x) ){

        $zz++;     
        $b = substr((string)$zz, -1);
    }

    return $zz;
}

$array[] = 243;
$array[] = 247;
$array[] = 249;
$array[] = 240;
$array[] = 250;

foreach($array as $row){

     print rounder($row)."<Br>";

}
unset($row);

========================

Output:

245
249
249
245
255

This can probably be shortened down to a few lines of code..... but whatever