How to check whether a variable in $_GET Array is

问题:

I have a page like so:

http://sitename/gallery.php?page=2

It has pagination links at the bottom by which we can browse. Everytime the page numbers are clicked, it would send a GET request with parameters page=1 or page=2 and so on ...

When I store these values to $page from teh $_GET variable, it is a string value. I can convert it to an integer using (int) like this:

if(!empty($_GET['page'])){
       $page = (int)$_GET['page'];
       echo "Page Number: ".$page;
}

But how can I make sure that the value passed is an integer only and not other crap?

回答1:

Using filters:

if (null !== ($page = filter_input(INPUT_GET, 'page', FILTER_VALIDATE_INT, FILTER_NULL_ON_FAILURE))) {
    // $page is now an integer
}

This also checks whether the variable appears in the query string at the same time. If you want to differentiate between missing and invalid you have to leave off the last argument to filter_input():

$page = filter_input(INPUT_GET, 'page', FILTER_VALIDATE_INT);
// $page can be null (not present), false (present but not valid) or a valid integer

回答2:

Use filter_var() with the FILTER_VALIDATE_INT filter on it, and check the return value.

回答3:

Use is_numeric().

is_int() will not work because GET parameters are always string.

回答4:

I've left a few comments here and there. Thanks to weak typing, functions like empty and isset tend to be unreliable. The quickest way to check if a parameter is an int or not IMO would be this:

if (array_key_exists('page',$_GET) && ($_GET['page'] == (int) $_GET['page']))

Casting to int and then compare the respective values will return true only when $_GET['page'] is a valid int. If you want to use strict type comparison for some reason (some do), you could double cast:

if (array_key_exists('page',$_GET) && ($_GET['page'] === (string)((int) $_GET['page'])))

But in this particular case, I can't really see why you would want to do that

回答5:

this is a way how to check parameter if it is intetger or not.

if (is_int((int) $_GET['user_id']) && (int) $_GET['user_id'] != 0) {
    $user_id = $_GET['user_id'];
}

回答6:

Using is_int won't help, probably. All incoming parameters (including $_GET and $_POST) are parsed as strings by PHP. The is_int function checks the datatype, not the value. ctype_digit checks for only digits though:

if(isset($_GET['page']) && ctype_digit($_GET['page']){
   $page = (int)$_GET['page'];
   echo "Page Number: ".$page;
}

回答7:

if(!empty($_GET['page']) and is_numeric($_GET['page'])){
       $page = (int)$_GET['page'];
       echo "Page Number: ".$page;
}

is_numeric is probably what you need.

回答8:

You can also check with

isNAN($_GET['something']);//is_numeric($_GET['something'])

it returns a boolean value(true,flase)....if its true then it is not an integer,if false its an integer.

回答9:

if (isset($_GET['page']) && (($get_page_filtered = filter_var($_GET['page'], FILTER_VALIDATE_INT)) !== FALSE) {
  $get_page_int = $get_page_filtered;
}

@see https://stackoverflow.com/a/41868665/6758130