如何进行数字轮？

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

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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