[RESOLVED] is is_int() buggy or logic flaw or..?

ppowell

Consider this code:

$willShowAnchorTag = !(
				 (isset($_REQUEST['sort']) && (int)$_REQUEST['sort'] === $i) ||
				 (!isset($_REQUEST['sort']) && $i === 0)
			        );

Here are your results:

1) If $REQUEST['sort'] does not exist and $i == 0 => $willShowAnchorTag = FALSE
2) If $REQUEST['sort'] does not exist and $i != 0 => $willShowAnchorTag = TRUE
3) If $REQUEST['sort'] == $i && $i == 0 => $willShowAnchorTag = FALSE
4) If $REQUEST['sort'] == $i && $i != 0 => $willShowAnchorTag = TRUE

OK, all of that is logically accurate and exactly what I want.

However, consider this: I replace isset() with is_int() and watch what happens this time:

$willShowAnchorTag = !(
				 (is_int($_REQUEST['sort']) && (int)$_REQUEST['sort'] === $i) ||
				 (!is_int($_REQUEST['sort']) && $i === 0)
			        );

1) If $REQUEST['sort'] does not exist and $i == 0 => $willShowAnchorTag = FALSE
2) If $REQUEST['sort'] does not exist and $i != 0 => $willShowAnchorTag = TRUE
3) If $REQUEST['sort'] == $i && $i == 0 => $willShowAnchorTag = TRUE
4) If $REQUEST['sort'] == $i && $i != 0 => $willShowAnchorTag = FALSE

Nos 3) and 4) are wrong, but why?? If $REQUEST['sort'] is an integer, then is_int() should detect that and indicate Boolean true or false, but it doesn't, yet isset() does (isset() is VERY unsafe because $REQUEST['sort'] then could be a string, an object, anything!)

Any ideas?

Phil

crazychris

all POST and GET are strings, no matter what they contain. Use is_numeric() instead of is_int()

ppowell

crazychris wrote:
all POST and GET are strings, no matter what they contain. Use is_numeric() instead of is_int()

I realize this, however, in PHP, everything scalar is a string. Because in PHP scalar values are always strings, but take on roles based upon configuration

'1' == 1 && '1' == true
'1' !== 1 && '1' !== true

So is_int(), according to the manual, determines if a parameter is an integer. That means it has to determine if a STRING parameter input '1' is an integer, and yet it doesn't, which is utterly illogical based upon PHP's initial definition of scalar content.

I will try is_numeric(), but that will then fail if I enter in "1.25" instead of "1" (it's supposed to be integer only)

Phil

frost110

use strstr So setup the equation like.


if (is_numeric($num) && !strstr($num, ".")) {
    print "It is an Int!";
}else {
    print "not an Int";
}

As for is_int I do believe it is a buggy function. I have never had it work EVER.

--FrosT

ppowell

hasn't yet been reported to bugs.php.net AFAIK based on the Manual.

Phil

crazychris

is_int() does work, but only for a variable CAST as an integer. The variables sent via POST/GET are all cast as strings, no matter what they contain, so will be able to be used as an integer, but are really strings.

<?php
if ($_POST['testvar']) {
	$a=$_POST['testvar'];
	$b=(int)$_POST['testvar'];
	if (is_int($a)) {
		print "A is INT";
	}
	if (is_int($b)) {
		print "B is INT";
	}
}
?>

If a number is sent in testvar, then result will be : "B is INT"

Drakla

[man]ctype_digit[/man]

Weedpacket

ppowell wrote:
That means it has to determine if a STRING parameter input '1' is an integer, and yet it doesn't

Of course not. Because a string is not an integer. It's called is_int() and not is_scalar() or is_string_that_looks_like_an_integer_when_you_print_it_out() for a reason.

$a = '1'; // $a contains a string, not an integer.
$a = 1; // $a contains an integer, not a string.

I think you need to learn what [man]Types[/man] are.

[man]Types[/man]
PHP supports eight primitive types.
Four scalar types:

boolean
integer
float (aka double)
string

Observe how integers and strings have their own entries.

ppowell

Weedpacket wrote:
Of course not. Because a string is not an integer. It's called is_int() and not is_scalar() or is_string_that_looks_like_an_integer_when_you_print_it_out() for a reason.
$a = '1'; // $a contains a string, not an integer.
$a = 1; // $a contains an integer, not a string.
[snip]

Ok, then explain this, please:
<?

  $a = 1;
  print_r("a = $a and strlen(\$a) = " . strlen($a) . " oh and ($a == '1')? " . ($a == '1'));

  // PRODUCES a = 1 and strlen($a) = 1 oh and (1 == '1')? 1

?>
How can one do a string length on an integer? By definition, an integer is NOT a string, and yet, strangely enough, I can do that, unless $a has always BEEN a string that takes the role of an integer data type because it just so happens to LOOK like the integer 1.

I understand types all too well, unless PHP redefines logic relativistically to say that an integer by definition is a type of string, which in other languages are distinct datatypes.

Phil

ppowell

Once more, this time I even CAST it as an integer, and watch this:

<?

  $a = 1;
  print_r("<P>a = $a and strlen(\$a) = " . strlen($a) . " oh and ($a == '1')? " . ($a == '1') . " is int? " . is_int($a));
  $a = (int)1;
  print_r("<P>a = $a and strlen(\$a) = " . strlen($a) . " oh and ($a == '1')? " . ($a == '1') . " is int? " . is_int($a));
?>

Produces:

a = 1 and strlen($a) = 1 oh and (1 == '1')? 1 is int? 1

a = 1 and strlen($a) = 1 oh and (1 == '1')? 1 is int? 1

Phil

ppowell

Drakla wrote:
[man]ctype_digit[/man]

Thank you!
Phil

laserlight

How can one do a string length on an integer?

The integer is implicitly converted to a string, and the string length is taken. Read the PHP Manual on strings, in particular the section on converting to string.

Once more, this time I even CAST it as an integer

Recall that the == operator tests for equality of value. You should use the === operator in your test, since you want to test for equality of both value and type. Also, (int)1 is rather silly since you're typecasting an integer literal to an integer.

dream_scape

I suggest you might want read the manual more carefully. 😉 This note on the is_int() page is sitting there plain as day:

Note: To test if a variable is a number or a numeric string (such as form input, which is always a string), you must use is_numeric().

Also why do you wish to use is_int() and not isset()? First off, if you do that, and $_REQUEST['sort'] does not exist, you will get an undefined variable notice. (that is why we use isset() in the first place, to be sure a variable does exist). Secondly, you then typecast it to an integer when checking it against $i, so what does it matter if it is not truly an integer? Anything not a numeric string will translate to 0:

PowerBook-G4:~ dream.scape$ php -a
Interactive mode enabled

php > $sort = 'I will hack you';
php > echo (int)$sort;

php >

ppowell

Your explanation would make sense, were it not for the fact that $sort HAS to be an integer ONLY, because if it evaluates to anything else, a back-end "bad query string crap eraser" will erase it, because it's restricted due to government-level security requirement blah blah blah..

And it handles differently if $sort === NULL.

Phil

dream_scape

so if it has to be an integer only, then typecast it to an integer prior to running the checks.

$_REQUEST['sort'] = (int)$_REQUEST['sort']

I believe you are trying to make things more difficult than they are. every question and supposed "bug" or logical flaw you've tried to demonstrate, is clearly explained in the manual the way it works in the language. I know you've said you have read the manual, but frankly from all your ranting I am inclined to believe otherwise.

ppowell

dream.scape wrote:
so if it has to be an integer only, then typecast it to an integer prior to running the checks.
$_REQUEST['sort'] = (int)$_REQUEST['sort']
I believe you are trying to make things more difficult than they are. every question and supposed "bug" or logical flaw you've tried to demonstrate, is clearly explained in the manual the way it works in the language. I know you've said you have read the manual, but frankly from all your ranting I am inclined to believe otherwise.

Thanx for your assumption, albeit inaccurate.

I should point out that in the thread earlier, $REQUEST values are strings, so casting as an integer is pointless as it will still be a string. And even if somehow it "becomes" an integer, then I'm still able to do strlen() and string functions on what is supposed to be an integer, which then infers to the idea that the value of $REQUEST['sort'] is really a string that happens to take the role and form of an integer.

So again, how is something both absolutely defined as two entirely different datatypes at the same time?

Phil

dream_scape

REQUEST variables are sent as strings. Once you have got them, you can change them. typecasting $_REQUEST['sort'] to an integer will make it an integer datatype.

Also, integers can be use in some string operations and strings can be used in some integer operations because PHP is a loosely (or weakly if you prefer), dynamically typed language.

If you need such restrictions that a variable typecast as an integer can function only and only as an integer without exception, then you are working with the wrong language my friend. You need to seek a strongly typed language that provide the datatyping restrictions you require in that case. (Java might be a good place to start)

crazychris

To quote my PHP Manual:

Type Juggling
PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which that variable is used. That is to say, if you assign a string value to variable $var, $var becomes a string. If you then assign an integer value to $var, it becomes an integer.

An example of PHP's automatic type conversion is the addition operator '+'. If any of the operands is a float, then all operands are evaluated as floats, and the result will be a float. Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does NOT change the types of the operands themselves; the only change is in how the operands are evaluated.

<?php
$foo = "0";  // $foo is string (ASCII 48)
$foo += 2;   // $foo is now an integer (2)
$foo = $foo + 1.3;  // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs";     // $foo is integer (15)
?>

String conversion to numbers
When a string is evaluated as a numeric value, the resulting value and type are determined as follows.

The string will evaluate as a float if it contains any of the characters '.', 'e', or 'E'. Otherwise, it will evaluate as an integer.

The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits.

<?php
$foo = 1 + "10.5";                // $foo is float (11.5)
$foo = 1 + "-1.3e3";              // $foo is float (-1299)
$foo = 1 + "bob-1.3e3";           // $foo is integer (1)
$foo = 1 + "bob3";                // $foo is integer (1)
$foo = 1 + "10 Small Pigs";       // $foo is integer (11)
$foo = 4 + "10.2 Little Piggies"; // $foo is float (14.2)
$foo = "10.0 pigs " + 1;          // $foo is float (11)
$foo = "10.0 pigs " + 1.0;        // $foo is float (11)     

?>

For more information on this conversion, see the Unix manual page for strtod(3).

laserlight

so if it has to be an integer only, then typecast it to an integer prior to running the checks.

Of course, the suggestion of using ctype_digit() will also do, though the approach is somewhat different.

I should point out that in the thread earlier, $REQUEST values are strings, so casting as an integer is pointless as it will still be a string.

That cannot be so, otherwise typecasting would have no effect in the general case. Consider this example:

<?php
if (isset($_REQUEST['foo'])) {
	//test if $_REQUEST['foo'] is of int type and has value 2
	if ($_REQUEST['foo'] === 2) {
		echo 'foo is an integer of value 2<br />';
	} else {
		echo 'foo is not an integer of value 2<br />';
	}

//typecast $_REQUEST['foo'] to int
$_REQUEST['foo'] = (int)$_REQUEST['foo'];

//test if $_REQUEST['foo'] is of int type and has value 2
if ($_REQUEST['foo'] === 2) {
	echo 'foo is an integer of value 2';
} else {
	echo 'foo is not an integer of value 2';
}
} else {
	echo 'foo is not set, or is null';
}
?>

And even if somehow it "becomes" an integer, then I'm still able to do strlen() and string functions on what is supposed to be an integer, which then infers to the idea that the value of $_REQUEST['sort'] is really a string that happens to take the role and form of an integer.

I told you to read the PHP Manual on the string datatype, and even provided the link to the relevant page. You are advised to RTFM now, even if you did so earlier. After you have finished reading up on the string datatype, proceed to read the PHP Manual on types in general. If you come back to ask before you have finished reading all of it, you will be zapped by my intense laser. Yes, burnt to a crisp. You have been warned.

ppowell

I have, and guess what, it makes no sense to me, and because the matter has been resolved, I shall proceed no further.

I have a feeling that PHP Builder community views the logic behind the CONCEPT of types differently and more relativsitically than I.

Phil