How to check if string value returned from text input is integer

Question

I have a form where users search for keywords.

I want to check if users submit a number (integer) instead of a keyword.

I use this:

$keyword = $_REQUEST["keyword"];

if (is_int($keyword)) {
  echo 'true';
} else {
  echo 'false';
}

but it always returns false even when the value submitted is integer.

That's because `$_POST` always contains strings, not integer values. — Michael Berkowski, Feb 23 '12 at 16:18
I tend to use [`ctype_digit()`](http://us3.php.net/manual/en/function.ctype-digit.php), but people do it lots of different ways. — Michael Berkowski, Feb 23 '12 at 16:18
possible duplicate of [php validate integer](http://stackoverflow.com/questions/4100022/php-validate-integer) — Michael Berkowski, Feb 23 '12 at 16:19
possible duplicate of [How can I limit the max value of number?](http://stackoverflow.com/questions/9414851/how-can-i-limit-the-max-value-of-number) — Your Common Sense, Feb 23 '12 at 16:20

score 9 · Accepted Answer · answered Feb 23 '12 at 16:19

9

is_int checks to see whether the variable is of integer type. What you have is a string whose characters happen to represent an integer.

Try:

if (is_numeric($keyword) && is_int(0+$keyword))

The 0+ will implicitly convert the following to a number type, so you'll end up with the numeric value of the string if possible. Calling is_numeric first ensures you aren't converting garbage.

answered Feb 23 '12 at 16:19

Borealid

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there are many ways to do this but personally i prefer *explicit* conversions over *implicit* ones because they are much more expressive. also checking for the maximum integer size is a good idea. – Kaii Feb 23 '12 at 16:35

Kaii · Answer 2 · 2012-02-23T16:35:58.873

is_int() is for type safe comparison, so the string that is received from the browser always evaluates to false.

If you really need to check if a variable is an integer you can use this handy function:

function str_is_int($number) {
    // compare explicit conversion to original and check for maximum INT size
    return ( (int)$number == $number && $number <= PHP_INT_MAX );  
    // will return false for "123,4" or "123.20"
    // will return true for "123", "-123", "-123,0" or "123.0"
}

Note: you should replace PHP_INT_MAX with the maximum integer size of your target system - e.g. your database.

in the docs of is_int() you can read this:

is_int — Find whether the type of a variable is integer

bool is_int ( mixed $var )

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().

Example:

<?php
if (is_int(23)) {
    echo "is integer\n";
} else {
    echo "is not an integer\n";
}
var_dump(is_int(23));
var_dump(is_int("23"));
var_dump(is_int(23.5));
var_dump(is_int(true));
?>

The above example will output:

is integer
bool(true)
bool(false)
bool(false)
bool(false)

is_numeric() works but I need to know also if number is integer. — Yannis, Feb 23 '12 at 16:18

score -1 · Answer 3 · edited May 09 '16 at 04:24

-1

I think ctype_digit() will work in your case.

edited May 09 '16 at 04:24

Box Box Box Box

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answered Dec 06 '14 at 08:20

user2029645

1
1

Please give some details. Or Place it in comments. – Syeda Zunaira Dec 06 '14 at 08:24

How to check if string value returned from text input is integer

3 Answers3