PHP check if variable is a whole number

Question

I have this PHP code:

$entityElementCount = (-($highScore-$totalKeywordCount))/0.29;

What i want to know is, how to check whether $

Answer 1

I tested all the proposed solutions with many problematic values mentioned, they all fail for at least one of the test cases. Start checking if $value is a number using is_numeric($value) reduces the number of failures for many solutions, but does not turn any solution into an ultimate one:

$test_cases = array(0.29, 2, 6, 2.33, 6.2, '10.00', 1.4, 10, "10", 10.5, "0x539", true,
    false, 0x53, 9.4, "ten", "100", 1, 0.999999997, 0, 0.0001, 1.0, 0.9999999,
    (-(4.42-5))/0.29);

function is_whole_number($value) {
    // Doing this prevents failing for values like true or "ten"
    if (!is_numeric($value)) {
        return false;
    }

    // @ghostdog74's solution fails for "10.00"
    // return (ctype_digit((string) $value));

    // Both @Maurice's solutions fails for "10.00"
    // return ((string) $value === (string) (int) $value);
    // return is_int($value);

    // @j.hull's solution always returns true for numeric values
    // return (abs($value) % 1 == 0 ? true : false);

    // @ MartyIX's solution fails for "10.00"
    // return ($value === intval($value));

    // This one fails for (-(4.42-5))/0.29
    // return (floor($value) == $value);

    // This one fails for 2
    // return ctype_digit($value);

    // I didn't understand Josh Crozier's answer

    // @joseph4tw's solution fails for (-(4.42-5))/0.29
    // return !(fmod($value, 1) != 0);

    // If you are unsure about the double negation, doing this way produces the same
    // results:
    // return (fmod($value, 1) == 0);

    // Doing this way, it always returns false 
    // return (fmod($value, 1) === 0);

    // @Anthony's solution fails for "10.00"
    // return (is_numeric($value) && is_int($value));

    // @Aistina's solution fails for 0.999999997
    // return (abs($value - round($value)) < 0.0001);

    // @Notinlist's solution fails for 0.999999997
    // return (round($value, 3) == round($value));
}

foreach ($test_cases as $test_case) {
    var_dump($test_case);
    echo ' is a whole number? ';
    echo is_whole_number($test_case) ? 'yes' : 'no';
    echo "\n";
}

I think that solutions like the ones proposed by @Aistina and @Notinlist are the best ones, because they use an error threshold to decide whether a value is a whole number. It is important to note that they worked as expected for the expression (-(4.42-5))/0.29, while all the others failed in that test case.

I decided to use @Notinlist's solution because of its readability:

function is_whole_number($value) {
    return (is_numeric($value) && (round($value, 3) == round($value)));
}

I need to test if values are whole numbers, currency or percentage, I think 2 digits of precision is enough, so @Notinlist's solution fits my needs.

Running this test:

$test_cases = array(0.29, 2, 6, 2.33, 6.2, '10.00', 1.4, 10, "10", 10.5, "0x539", true,
    false, 0x53, 9.4, "ten", "100", 1, 0.999999997, 0, 0.0001, 1.0, 0.9999999,
    (-(4.42-5))/0.29);

function is_whole_number($value) {
    return (is_numeric($value) && (round($value, 3) == round($value)));
}

foreach ($test_cases as $test_case) {
    var_dump($test_case);
    echo ' is a whole number? ';
    echo is_whole_number($test_case) ? 'yes' : 'no';
    echo "\n";
}

Produces the following output:

float(0.29)
 is a whole number? no
int(2)
 is a whole number? yes
int(6)
 is a whole number? yes
float(2.33)
 is a whole number? no
float(6.2)
 is a whole number? no
string(5) "10.00"
 is a whole number? yes
float(1.4)
 is a whole number? no
int(10)
 is a whole number? yes
string(2) "10"
 is a whole number? yes
float(10.5)
 is a whole number? no
string(5) "0x539"
 is a whole number? yes
bool(true)
 is a whole number? no
bool(false)
 is a whole number? no
int(83)
 is a whole number? yes
float(9.4)
 is a whole number? no
string(3) "ten"
 is a whole number? no
string(3) "100"
 is a whole number? yes
int(1)
 is a whole number? yes
float(0.999999997)
 is a whole number? yes
int(0)
 is a whole number? yes
float(0.0001)
 is a whole number? yes
float(1)
 is a whole number? yes
float(0.9999999)
 is a whole number? yes
float(2)
 is a whole number? yes

Answer 2

Just to share my solution with localized string/number, this combo worked like a charm for me.

public static function isWholeNumber ($input, $decimalDelimiter = ',')
{
    if (is_string($input)){
        $input = str_replace($decimalDelimiter, '.', $input);
        $input = floatval($input);
    }

    if (fmod($input,1) !== 0.0) {
        return false;
    }

    return true;
}

Answer 3

if(floor($number) == $number)

Is not a stable algorithm. When a value is matematically 1.0 the numerical value can be 0.9999999. If you apply floor() on it it will be 0 which is not equals to 0.9999999.

You have to guess a precision radius for example 3 digits

if(round($number,3) == round($number))

Answer 4

function isInteger($value)
{
    // '1' + 0 == int, '1.2' + 0 == float, '1e2' == float
    return is_numeric($value) && is_int($value + 0);
}

function isWholeNumber($value)
{
    return is_numeric($value)
        && (is_int($value + 0)
            || (intval($value + 0) === intval(ceil($value + 0))));
}

If you want to check for both whole and decimal numbers, you can do the following:

if (isInteger($foo))
{
    // integer as int or string
}
if (isWholeNumber($foo))
{
    // integer as int or string, or float/double with zero decimal part
}
else if (is_numeric($foo))
{
    // decimal number - still numeric, but not int
}

This will correctly check your number without rounding it, casting it to int (which in the case of a decimal number will lose the decimal part), or doing any math. If, however, you want to treat 1.00 as a whole number, then that's a whole another story.

Answer 5

If you know that it will be numeric (meaning it won't ever be a an integer cast as a string, like "ten" or "100", you can just use is_int():

$entityElementCount = (-($highScore-$totalKeywordCount))/0.29;
$entityWholeNumber = is_int($entityElementCount);

echo ($entityWholeNumber) ? "Whole Number!" : "Not a whole number!";

Answer 6

A simple solution for positive whole numbers only. This may not work for everything.

$string = '0x539';
$ceil = ceil($string);

if($ceil < 1){
  $ceil = FALSE; // or whatever you want i.e 0 or 1
}

echo $ceil; // 1337

You can use floor() instead of ceil() if so desired.