CODEWITHSUNDEEP
php
andig
andig

Reputation: 13888

PHP: How to check if variable is a "large integer"

I need to check if a parameter (either string or int or float) is a "large" integer. By "large integer" I mean that it doesn't have decimal places and can exceed PHP_INT_MAX. It's used as msec timestamp, internally represented as float.

ctype_digit comes to mind but enforces string type. is_int as secondary check is limited to PHP_INT_MAX range and is_numeric will accept floats with decimal places which is what I don't want.

Is it safe to rely on something like this or is there a better method:

if (is_numeric($val) && $val == floor($val)) {
    return (double) $val;
}
else ...

Upvotes: 13

Views: 5049

Answers (4)

user4308987
user4308987

Reputation:

I did at the end of the function to check for numeric data.

return is_numeric($text)&&!(is_int(strpos($text,".",0)));

It will first check if it is numeric then check if there is no decimal in the string by checking if it found a position. If it did the returned position is an int so is_int() will catch it.

(strpos($text,".",0)==FALSE) would also work based on the strpos manual but sometimes the function seems to send nothing at all back like

echo (strpos($text,".",0));

could be nothing and the ==FALSE is needed.

Upvotes: 0

takashiki
takashiki

Reputation: 1

function isInteger($var)
{
    if (is_int($var)) {
        return true;
    } elseif (is_numeric($var)) {
        // will throw warning
        if (!gmp_init($var)) {
            return false;
        } elseif (gmp_cmp($var, PHP_INT_MAX) >0) {
            return true;
        } else {
            return floor($var) == $var;
        }
    }
    return false;
}

Upvotes: 0

Ja͢ck
Ja͢ck

Reputation: 173642

So basically you want to check if a particular variable is integer-like?

function isInteger($var)
{
    if (is_int($var)) {
        // the most obvious test
        return true;
    } elseif (is_numeric($var)) {
        // cast to string first
        return ctype_digit((string)$var);
    }
    return false;
}

Note that using a floating point variable to keep large integers will lose precision and when big enough will turn into a fraction, e.g. 9.9999999999991E+36, which will obviously fail the above tests.

If the value exceeds INT_MAX on the given environment (32-bit or 64-bit), I would recommend using gmp instead and persist the numbers in a string format.

Upvotes: 4

Daniel W.
Daniel W.

Reputation: 32340

I recommend the binary calculator as it does not care about length and max bytes. It converts your "integer" to a binary string and does all calculations that way.

BC math lib is the only reliable way to do RSA key generation/encryption in PHP, and so it can easy handle your requirement:

$userNumber = '1233333333333333333333333333333333333333312412412412';

if (bccomp($userNumber, PHP_INT_MAX, 0) === 1) {
    // $userNumber is greater than INT MAX
}

Third parameter is the number of floating digits.

Upvotes: 6

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