Set precision for a float number in PHP

Question

I get a number from database and this number might be either float or int.

I need to set the decimal precision of the number to 3, which makes the number not longer than (regarding decimals) 5.020 or 1518845.756.

Using PHP

round($number, $precision)

I see a problem:

It rounds the number. I need a function to only cut the decimals short, without changing their values which round( ) seems not to follow.

Solution 1

You can use number_format() to achieve this:

echo number_format((float) $number, $precision, '.', ''); 

This would convert 1518845.756789 to 1518845.757.

But if you just want to cut off the number of decimal places short to 3, and not round, then you can do the following:

$number = intval($number * ($p = pow(10, $precision))) / $p;

It may look intimidating at first, but the concept is really simple. You have a number, you multiply it by 10³ (it becomes 1518845756.789), cast it to an integer so everything after the 3 decimal places is removed (becomes 1518845756), and then divide the result by 10³ (becomes 1518845.756).

Demo

Solution 2

Its sound like floor with decimals. So you can try something like

floor($number*1000)/1000

Solution 3

If I understand correctly, you would not want rounding to occur and you would want the precision to be 3.

So the idea is to use number_format() for a precision of 4 and then remove the last digit:

$number = '1518845.756789';
$precision = 3;

echo substr(number_format($number, $precision+1, '.', ''), 0, -1);

Will display:

1518845.756

rather than:

1518845.757

Links : number_format() , substr()

Solution 4

See this answer for more details.

function numberPrecision($number, $decimals = 0)
{
    $negation = ($number < 0) ? (-1) : 1;
    $coefficient = pow(10, $decimals);
    return $negation * floor((string)(abs($number) * $coefficient)) / $coefficient;
}

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