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PHP: get number of decimal digits

Posted by: admin November 29, 2017 Leave a comment

Questions:

Is there a straightforward way of determining the number of decimal places in a(n) integer/double value in PHP? (that is, without using explode)

Thanks,

Erwin

Answers:
$str = "1.23444";
print strlen(substr(strrchr($str, "."), 1));

Questions:
Answers:

You could try casting it to an int, subtracting that from your number and then counting what’s left.

Questions:
Answers:
function numberOfDecimals($value)
{
    if ((int)$value == $value)
    {
        return 0;
    }
    else if (! is_numeric($value))
    {
        // throw new Exception('numberOfDecimals: ' . $value . ' is not a number!');
        return false;
    }

    return strlen($value) - strrpos($value, '.') - 1;
}


/* test and proof */

function test($value)
{
    printf("Testing [%s] : %d decimals\n", $value, numberOfDecimals($value));
}

foreach(array(1, 1.1, 1.22, 123.456, 0, 1.0, '1.0', 'not a number') as $value)
{
    test($value);
}

Outputs:

Testing [1] : 0 decimals
Testing [1.1] : 1 decimals
Testing [1.22] : 2 decimals
Testing [123.456] : 3 decimals
Testing [0] : 0 decimals
Testing [1] : 0 decimals
Testing [1.0] : 0 decimals
Testing [not a number] : 0 decimals

Questions:
Answers:

I used the following to determine whether a returned value has any decimals (actual decimal values, not just formatted to display decimals like 100.00):

if($mynum - floor($mynum)>0) {has decimals;} else {no decimals;} 

Questions:
Answers:

Something like:

<?php

$floatNum = "120.340304";
$length = strlen($floatNum);

$pos = strpos($floatNum, "."); // zero-based counting.

$num_of_dec_places = ($length - $pos) - 1; // -1 to compensate for the zero-based count in strpos()

?>

This is procedural, kludgy and I wouldn’t advise using it in production code. But it should get you started.

Questions:
Answers:
<?php

test(0);
test(1);
test(1.234567890);
test(-123.14);
test(1234567890);
test(12345.67890);

function test($f) {
    echo "f = $f\n";
    echo "i = ".getIntCount($f)."\n";
    echo "d = ".getDecCount($f)."\n";
    echo "\n";
}

function getIntCount($f) {
    if ($f === 0) {
        return 1;
    } elseif ($f < 0) {
        return getIntCount(-$f);
    } else {
        return floor(log10(floor($f))) + 1;
    }
}

function getDecCount($f) {
    $num = 0;
    while (true) {
        if ((string)$f === (string)round($f)) {
            break;
        }
        if (is_infinite($f)) {
            break;
        }

        $f *= 10;
        $num++;
    }
    return $num;
}

Outputs:

f = 0
i = 1
d = 0

f = 1
i = 1
d = 0

f = 1.23456789
i = 1
d = 8

f = -123.14
i = 3
d = 2

f = 1234567890
i = 10
d = 0

f = 12345.6789
i = 5
d = 4

Questions:
Answers:
$decnumber = strlen(strstr($yourstr,'.'))-1

Questions:
Answers:

How about this?:

$iDecimals = strlen($sFull%1);

Questions:
Answers:

Here’s a function that takes into account trailing zeroes:

function get_precision($value) {
    if (!is_numeric($value)) { return false; }
    $decimal = $value - floor($value); //get the decimal portion of the number
    if ($decimal == 0) { return 0; } //if it's a whole number
    $precision = strlen($decimal) - 2; //-2 to account for "0."
    return $precision; 
}

Questions:
Answers:

Int

Integers do not have decimal digits, so the answer is always zero.

Double/Float

Double or float numbers are approximations. So they do not have a defined count of decimal digits.

A small example:

$number = 12.00000000012;
$frac = $number - (int)$number;

var_dump($number);
var_dump($frac);

Output:

float(12.00000000012)
float(1.2000000992884E-10)

You can see two problems here, the second number is using the scientific representation and it is not exactly 1.2E-10.

String

For a string that contains a integer/float you can search for the decimal point:

$string = '12.00000000012';
$delimiterPosition = strrpos($string, '.');
var_dump(
  $delimiterPosition === FALSE ? 0 : strlen($string) - 1 - $delimiterPosition
);

Output:

int(11)

Questions:
Answers:

I needed a solution that works with various number formats and came up with the following algorithms:

// Count the number of decimal places
$current = $value - floor($value);
for ($decimals = 0; ceil($current); $decimals++) {
    $current = ($value * pow(10, $decimals + 1)) - floor($value * pow(10, $decimals + 1));
}

// Count the total number of digits (includes decimal places)
$current = floor($value);
for ($digits = $decimals; $current; $digits++) {
    $current = floor($current / 10);
}

Results:

input:    1
decimals: 0
digits:   1

input:    100
decimals: 0
digits:   3

input:    0.04
decimals: 2
digits:   2

input:    10.004
decimals: 3
digits:   5

input:    10.0000001
decimals: 7
digits:   9

input:    1.2000000992884E-10
decimals: 24
digits:   24

input:    1.2000000992884e6
decimals: 7
digits:   14

Questions:
Answers:
$value = 182.949;

$count = strlen(abs($value - floor($value))) -2; //0.949 minus 2 places (0.)

Questions:
Answers:

First I have found the location of the decimal using strpos function and increment the strpos postion value by 1 to skip the decimal place.

Second I have subtracted the whole string length from the value I have got from the point1.

Third I have used substr function to get all digits after the decimal.

Fourth I have used the strlen function to get length of the string after the decimal place.

This is the code that performs the steps described above:

     <?php
        $str="98.6754332";
        echo $str;
        echo "<br/>";
        echo substr( $str, -(strlen($str)-(strpos($str, '.')+1)) );
        echo "<br/>";
        echo strlen( substr( $str, -(strlen($str)-(strpos($str, '.')+1))) );
    ?>

Questions:
Answers:

Solution

$num = "12.1234567";
print strlen(preg_replace("/.*\./", "", $num)); // 7

Explanation

Pattern “.*\.” means all the characters before the decimal point with its.

In this case it’s string with three characters: “12.“.

preg_replace function converts these characters to an empty string (second parameter).

In this case we get this string: “1234567“.

strlen function counts the number of characters in the above string.