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

Rather than checking for int OR string with multiple conditions like:

if ( ctype_digit($i) || ( is_int($i) && $i > 0 ) )
{
    return TRUE;
}

you can simplify this by just casting the input to (string) so that the one ctype_digit call will check both string and int inputs:

if( ctype_digit( (string)$i ) )
{
    return TRUE;
}

Answer 2

All these answers overlook the fact that the requestor may checking form input.
The is_int() will fail because the form input is a string.
is_numeric() will be true also for float numbers.
That is why the $i == round($i) comes in as it checks for the input being a whole number.

Answer 3

In addition to all the other answers: You are probably looking for ctype_digit. It looks for a string containing only digits.

Answer 4

The other best way to check a Integer number is using regular expression. You can use the following code to check Integer value. It will false for float values.

if(preg_match('/^\d+$/',$i)) {
  // valid input.
} else {
  // invalid input.
}

It's better if you can check whether $i > 0 too.

Answer 5

the difference between your two code snippets is that is_numeric($i) also returns true if $i is a numeric string, but is_int($i) only returns true if $i is an integer and not if $i is an integer string. That is why you should use the first code snippet if you also want to return true if $i is an integer string (e.g. if $i == "19" and not $i == 19).

See these references for more information:

php is_numeric function

php is_int function

Answer 6

    preg_match('{^[0-9]*$}',$string))

and if you want to limit the length:

    preg_match('{^[0-9]{1,3}$}',$string)) //minimum of 1 max of 3

So pisitive int with a max length of 6:

    if(preg_match('{^[0-9]{1,6}$}',$string)) && $string >= 0)