Best way to filtering to only integers?

[dannyb785]

Basically, the function I've been using to filter input to only integers is:

 

function make_int($input)
{
return (int)$input;
}

 

But I was wondering if it was better to use regex like preg_match... is my way sufficient or perhaps is one or the other harder on resources?

[Psycho]

No, regex would be a waste. But, that function is pretty much useless since you can just as easily use (int) $var instead of calling the function. You've basically created a function that does something that already exists.

[peipst9lker]

You're not filtering you're casting? Is that what you meant?

Filtering would be is_int(), is_numeric(), preg_match()

The function you provided is casting any value to an integer.

[xyph]

<?php

$var = 1235523;

$var2 = -245;

$var3 = 'apple';

var_dump( isInt($var) ); // boolean true
var_dump( isInt($var2) ); // boolean true
var_dump( isInt($var3) ); // boolean false

function isInt( $var ) {
$var = (string)$var;
if( ctype_digit($var) || ($var[0] == '-' && ctype_digit(substr($var,1))) )
	return TRUE;
return FALSE;
}

?>

[peipst9lker]

@xyph isn't is_numeric() doing the same thing?

[xyph]

No, the manual tells you that. Floats are numeric, but they aren't integers.

[dannyb785]

No, regex would be a waste. But, that function is pretty much useless since you can just as easily use (int) $var instead of calling the function. You've basically created a function that does something that already exists.

 

I get what you're saying, but I only made it a function so that if I discovered that the function had a flaw in it that I could easily change it and not have to manually change every time I did that action on every page.

 

And about casting/filtering: I just need to make sure that the specific input is an integer and convert it to an integer if it's not. So if it was "9 lbs" that the result would be '9', and similar

[scootstah]

No, the manual tells you that. Floats are numeric, but they aren't integers.

 

So why not use is_int?

[xyph]

No, the manual tells you that. Floats are numeric, but they aren't integers.

 

So why not use is_int?

 

Because PHP is loosely-typed, and generally variables coming from outside sources will be a string.

 

It really depends how detailed you want your error reporting. Casting as an integer will close many potential attack vectors, but there's no way of knowing if the value being cast as an integer was actually an integer-equivalent prior to.

 

I think you're taking my post out of context though. I was responding directly to this

@xyph isn't is_numeric() doing the same thing?

 

I should've made that more clear.