testing if php string is an integer

Question

$post is used to simulate $_POST, and I found that $_POST['int'] is a string.

How can I tell whether $post['int'] is an integer?

The following indicates that it is not an integer.

<?php
 $post=array('int'=>(string)123);
 var_dump($post);
 echo(is_int($post['int'])?'int':'not int');
?>

EDIT. Per the documentation (http://php.net/manual/en/function.is-int.php), is_int — Find whether the type of a variable is integer, so obviously it does exactly what it is suppose to do. Still need to tell whether the string is an integer...

Answer 1

If you really want to know if the value is an integer you can use filter_input(). Important: you can not test this with a fake $_POST var, you really have to post the value or use INPUT_GET for testing and append ?int=344 to your URL

// INPUT_POST => define that the input is the $_POST var
// 'int' => the index of $_POST you want to validate i.e. $_POST['int']
// FILTER_VALIDATE_INT => is it a valid integer
filter_input( INPUT_POST, 'int', FILTER_VALIDATE_INT );

Working example:

<form action="" method="post">
 <input type="text" name="int" />
 <input type="submit" />
</form>
<?php
if( isset( $_POST["int"] ) ) {
 echo( filter_input( INPUT_POST, 'int', FILTER_VALIDATE_INT ) ) ? 'int' : 'not int';
}

Update: Due to the comment of @user1032531's answer

I would have thought a baked-in solution would have been available

There is a built in function called filter_var(), that function does the same like the above example, but it doesn't need a POST or GET, you can simply pass a value or variable to it:

var_dump( filter_var ( 5, FILTER_VALIDATE_INT ) );// 5
var_dump( filter_var ( 5.5, FILTER_VALIDATE_INT ) );// false
var_dump( filter_var ( "5", FILTER_VALIDATE_INT ) );// 5
var_dump( filter_var ( "5a", FILTER_VALIDATE_INT ) );// false

• Chiwda: Thumbs up for filter_var - very powerful and even allows checks like valid email (FILTER_VALIDATE_EMAIL)

Answer 2

You can use is_numeric function it returns true if a var is integer or String Integer

<?php
 if(is_numeric($post)){
 //Its a number
 }
 else{
 //Not a number
 }
?>

If you want to know if a variable is a integer and not a string integer you can use

<?php
 if(is_int($post)){
 //Its a number
 }
 else{
 //Not a number
 }
?>

To Check if the variable is a float you can use is_float();

<?php
 if(is_numeric($post)){
 //Its a number
 if(is_float($post)){
 //Its a floating point number
 }
 }
 else{
 //Not a number
 }
 ?>

• user1032531: So this will tell whether it a number, but not necessarily an integer.
• Skyyy: No a number can be an integer and string both. I you want them to be integer or string. Then when you declare a int don't put it in quotes then its a integer if you put it in quotes than it will be a string
• C3roe: is_numeric('1.5') and is_numeric('1.0E+35') would yield true as well – not sure if that’s what the OP wants. And as for is_int – values received via GET/POST are always strings.
• user1032531: So, check if it is numeric, then type cast it as an int, then compare the two?
• Skyyy: @cbroe i am not sure about that. @user1032531 those comparison will result same just use is_numeric to determine if its a String Number then if you wan to perform mathematical operation on it then convert it in INT. var string = (int) number;

Answer 3

Don't think it is a strong solution, but...

<?php
function is_string_an_int($v){
 return is_numeric($v)&&(int)$v==$v;
}
echo is_string_an_int(5)?'y':'n';
echo is_string_an_int(5.5)?'y':'n';
echo is_string_an_int('5')?'y':'n';
echo is_string_an_int('5a')?'y':'n';

• user1032531: @swidmann Thanks. I would have thought a baked-in solution would have been available.
• swidmann: you're welcome, and there is such a function: filter_var() will return the int if it's an int or false if it's not an int
• user1032531: @swidmann I liked your solution, but wasn't sure about having to only test on a URL, etc. Neve rmind. Just finished reading your edited answer :)
• Nor.Z: this says true for "123.0" == 123 ? Seems filter_var is more strict?

Answer 4

You have to use is_numeric()

From php site documentation

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().

I personnaly use since a while :

function isInteger( $nbr ) { 
 if( preg_match( "/^[-]?[0-9]+$/", $nbr ) > 0 ) { 
 return true;
 } 
 return false;
 }

Explanations about the regex:

/ begin of the regex 
^ the beginning of the string that you need to verify
[-]? an optionnal minus sign. No more that one sign.
[0-9]+ at least one digit
$ end of the string that you want to verify
/ end of the regex

• user1032531: Per your edited solution. I really need to get better at regex. Not sure it works (but expect it does since you've been using it for a while), and will test.

Answer 5

The following cod snippet worked for me

if (is_numeric($_POST['in'])) {
echo "numeric!";
} else {
echo "not numeric";
}