Test whether string is valid integer

[Paul E Collins]

Given a string variable (form input), how can I determine whether it
represents a valid integer?

is_numeric is true for floats as well as integers, and is_int always
fails on a string.

P.

[Rutger Claes]

Re: Test whether string is valid integer

Paul E Collins wrote:
[color=blue]
> Given a string variable (form input), how can I determine whether it
> represents a valid integer?
>
> is_numeric is true for floats as well as integers, and is_int always
> fails on a string.
>
> P.[/color]

intval( $string ) == $string

works for me...
--
Rutger Claes rgc@rgc.tld
Replace tld with top level domain of belgium to contact me pgp:0x3B7D6BD6
From listening comes wisdom and from speaking repentance.

[Paul E Collins]

Re: Test whether string is valid integer

"Paul E Collins" <find_my_real_a ddress@CL4.org> wrote:
[color=blue]
> Given a string variable (form input), how can I
> determine whether it represents a valid integer?[/color]

Okay, I've come up with a solution:

function isInteger($x)
{
return ($x === (string) (int) $x);
}

It returns false if $x has leading zeros, but that doesn't matter for
my purposes.

P.

[Justin Koivisto]

Re: Test whether string is valid integer

Rutger Claes wrote:
[color=blue]
> Paul E Collins wrote:
>
>[color=green]
>>Given a string variable (form input), how can I determine whether it
>>represents a valid integer?
>>
>>is_numeric is true for floats as well as integers, and is_int always
>>fails on a string.
>>[/color]
>
> intval( $string ) == $string
>
> works for me...[/color]

Depends on how strict you need to be...

intval($n)==$n will return TRUE if you have a float like 5.0

However, if you use:

intval($n)===$n

Then the string '5' would fail...

If you need to reject floats, but need to use strings as well, you'll
really need to do something like this (pulled from something I did a
couple years ago):

/**
* input_intval
*
* Takes a variable and returns the integer value that corresponds
* to the value. If the value cannot be represented by an integer,
* FALSE is returned.
*
* @param $n [mixed] Value to check.
* @result Returns an integer value or FALSE. Check for FALSE using
* if(input_intval ($n)===FALSE) in case of integer < 0 being
* returned.
**/
function input_intval($n ){
if(is_numeric($ n)){
if(is_int($n)){
return $n;
}else{
// this is a float...
if(intval($n)== $n){
return $n;
}else{
return FALSE;
}
}
}else{
return FALSE;
}
}

--
Justin Koivisto - spam@koivi.com

http://www.koivi.com

[Justin Koivisto]

Re: Test whether string is valid integer

Justin Koivisto wrote:
[color=blue]
> Rutger Claes wrote:
>[color=green]
>> Paul E Collins wrote:
>>
>>[color=darkred]
>>> Given a string variable (form input), how can I determine whether it
>>> represents a valid integer?
>>>
>>> is_numeric is true for floats as well as integers, and is_int always
>>> fails on a string.
>>>[/color]
>>
>> intval( $string ) == $string
>>
>> works for me...[/color]
>
>
> Depends on how strict you need to be...
>
> intval($n)==$n will return TRUE if you have a float like 5.0
>
> However, if you use:
>
> intval($n)===$n
>
> Then the string '5' would fail...
>
> If you need to reject floats, but need to use strings as well, you'll
> really need to do something like this (pulled from something I did a
> couple years ago):
>
> /**
> * input_intval
> *
> * Takes a variable and returns the integer value that corresponds
> * to the value. If the value cannot be represented by an integer,
> * FALSE is returned.
> *
> * @param $n [mixed] Value to check.
> * @result Returns an integer value or FALSE. Check for FALSE using
> * if(input_intval ($n)===FALSE) in case of integer < 0 being
> * returned.
> **/
> function input_intval($n ){
> if(is_numeric($ n)){
> if(is_int($n)){
> return $n;
> }else{
> // this is a float...
> if(intval($n)== $n){
> return $n;[/color]

Sorry, that should have been:

return intval($n);

I was getting too far ahead of myself typing it out...
[color=blue]
> }else{
> return FALSE;
> }
> }
> }else{
> return FALSE;
> }
> }
>[/color]


--
Justin Koivisto - spam@koivi.com

http://www.koivi.com

[Tony Marston]

Re: Test whether string is valid integer

Here is the code I use:

$integer = (int)$value;
if ((string)$value <> (string)$intege r) {
$this->errors[$field] = "Value is not an integer";
return $value;
} // if

--
Tony Marston

http://www.tonymarston.net

"Paul E Collins" <find_my_real_a ddress@CL4.org> wrote in message
news:cn0710$57d $1@titan.btinte rnet.com...[color=blue]
> Given a string variable (form input), how can I determine whether it
> represents a valid integer?
>
> is_numeric is true for floats as well as integers, and is_int always fails
> on a string.
>
> P.
>
>[/color]

[Ilija Studen]

Re: Test whether string is valid integer

Paul E Collins wrote:[color=blue]
> Given a string variable (form input), how can I determine whether it
> represents a valid integer?
>
> is_numeric is true for floats as well as integers, and is_int always
> fails on a string.
>
> P.[/color]

"Zero" sensitive function :) 5.0000 is integer 5.0001 is not...

<?php

function checkInteger($i nput) {

// Check type
if(is_integer($ input)) {
return true;
} // if

// Typecast
$in = (integer) $input;

// Check strlen
if(($in == $input) && (strlen($in) == strlen($input)) ) {
return true;

// No '.'?
} elseif(strpos($ input, '.') === false) {
return false;

// We have '.'
} else {

// One for dot, other for zeros
$dig_num = strlen($input) - strlen($in) - 1;

// Get zeros
$zeros = '.';
for($i = 0; $i < $dig_num; $i++) {
$zeros .= '0';
} // form

// Final check
return (string) $in . $zeros == $input ? true : false;

} // if

} // func checkInteger

// Test it with this code!
print checkInteger('5 .00000') ? 'OK, int' : 'Not OK';

?>