如何进行数字回合？

Question

I want 3000 for all these numbers:

3001 - 3500 - 3999

I want 40000 for all these numbers:

40000.3 - 40101 - 48000.8 - 49901

I want 20 for all these numbers:

21 - 25.2 - 29

---

There is two PHP function to make a digit round ( floor and round ) But none of them don't act exactly what I need .

Note: I don't know my number is contains how many digits. If fact it is changing.

Is there any approach to do that?

Answer 1

There are "many" ways how to achieve this. One is this:

<?php

echo roundNumber( 29 )."<br>";
echo roundNumber( 590 )."<br>";
echo roundNumber( 3670 )."<br>";
echo roundNumber( 49589 )."<br>";

function roundNumber( $number )
{
    $digitCount = floor( log10( $number ) ) ;
    $base10     = pow( 10, $digitCount );
    return floor( $number /  $base10 ) * $base10;
}
?>

The output is this:

20
500
3000
40000

Answer 2

This will work for any no. of digits. Try this:

$input = 25.45;

if (strpos($input, ".") !== FALSE) {
    $num = explode('.', $input);
    $len = strlen($num[0]);
    $input = $num[0];
} else {
    $len = strlen($input);
}

$nearest_zeroes = str_repeat("0", $len-1);

$nearest_round = '1'.$nearest_zeroes;

echo floor($input/$nearest_round) * $nearest_round;

The idea is when you round a 4 digit no, say 3999, $nearest_round should be 1000.

For 39990(5 digit), $nearest_round = 10000.

For 25(2 digit), $nearest_round = 10.

And so on.

So, the idea is to generate $nearest_round dynamically based on the no. of digits of $input.

Hope this helps.

Answer 3

PHP allows negative precision for round such as with: round(3993,-3);

Output: 3000

n    round(1111.1111,n)
==   ==================
 3   1111.111
 2   1111.11
 1   1111.1
 0   1111
-1   1110
-2   1100
-3   1000

W3S about round