Best way to check for positive integer (PHP)?

Question

I need to check for a form input value to be a positive integer (not just an integer), and I noticed another snippet using the code below:

$i = $user_input_v         


        

Answer 1

The best way for checking for positive integers when the variable can be INTEGER or STRING representing the integer:

 if ((is_int($value) || ctype_digit($value)) && (int)$value > 0 ) { // int }

is_int() will return true if the value type is integer. ctype_digit() will return true if the type is string but the value of the string is an integer.

The difference between this check and is_numeric() is that is_numeric() will return true even for the values that represent numbers that are not integers (e.g. "+0.123").

Answer 2

Definition:

!A = !is_numeric($i)
B = $i < 1
!C = $i != round($i)

Then...

!is_numeric($i) || $i < 1 || $i != round($i) is equal to !A || B || !C

So:

!A || B || !C = !A || !C || B

Now, using the deMorgan theorem, i.e. (!A || !C) = (A && C), then:

!A || !C || B = (A && C) || B

Now, note that A && C = is_numeric($i) && $i == round($i), but if $i == round($i) is TRUE, then is_numeric($i) is TRUE as well, so we can simplify A && C = C so,

(A && C) || B = C || B =

$i == round($i) || $i < 1

So you just need to use:

$i = $user_input_value;
if ($i == round($i) || $i < 1) {
  return TRUE;
}

Answer 3

if(isset($i) && is_int($i) && $i >= 0){ //0 is technically a postive integer I suppose
    return TRUE; //or FALSE I think in your case.
}

Answer 4

It's definitely heading towards the land of micro-optimisation, but hey: the code I'm working on chews through millions of items every day and it's Friday. So I did a little bit of experimenting...

for ($i = 0; $i < 1000000; $i++) {
    // Option 1: simple casting/equivalence testing
    if ((int) $value == $value && $value > 0) { ... }

    // Option 2: using is_int() and ctype_digit().  Note that ctype_digit implicitly rejects negative values!
    if ((is_int($value) && $value > 0) || ctype_digit($value)) { ... }

    // Option 3: regular expressions
    if (preg_match('/^\d+$/', $value)) { ... }
}

I then ran the above tests for both integer and string values

Option 1: simple casting/equivalence testing

• Integer: 0.3s
• String: 0.4s

Option 2: using is_int() and ctype_digit()

• Integer: 0.9s
• String: 1.45s

Option 3: regular expressions

• Integer: 1.83s
• String: 1.60s

Perhaps unsurprisingly, option 1 is by far the quickest, since there's no function calls, just casting. It's also worth noting that unlike the other methods, option 1 treats the string-float-integer value "5.0" as an integer:

$valList = array(5, '5', '5.0', -5, '-5', 'fred');
foreach ($valList as $value) {
    if ((int) $value == $value && $value > 0) {
        print "Yes: " . var_export($value, true) . " is a positive integer\n";
    } else {
        print "No: " . var_export($value, true) . " is not a positive integer\n";
    }
}

Yes: 5 is a positive integer
Yes: '5' is a positive integer
Yes: '5.0' is a positive integer
No: -5 is not a positive integer
No: '-5' is not a positive integer
No: 'fred' is not a positive integer

Whether or not that's a good thing for your particular use-case is left as an exercise for the reader...

Answer 5

You don't really need to use all three check and if you want a positive integer you might want to do the opposite of what is in your code:

if(is_numeric($i) && $i >= 0) { return true; }

Check Sören's answer for more information concerning the difference between is_int() and is_numeric()

Answer 6

Ok, I know this thread is really old but I share @Jeffrey Vdovjak's opinion: since I was able to find it, it might still help someone else out there.

php's gmp_sign() might be another easy way to check. It works for integer and numeric strings, and returns 1 if a is positive, -1 if a is negative, and 0 if a is zero.

So:

// positive
echo gmp_sign("500") . "\n";

// negative
echo gmp_sign("-500") . "\n";

// zero
echo gmp_sign("0") . "\n";

will output:

1
-1
0

See function manual at http://php.net/manual/en/function.gmp-sign.php

P.S. You'll need to have php_gmp.dll enabled in your .ini file.