Getting confused with empty, isset, !empty, !isset

Question

I have the following which doesn\'t work properly as $_GET[\'category\'] can also equal 0.

if ( empty( $_GET[\'category\'] ) ){
    // do something
         


        

Answer 1

This isn't really hard to do: isset is the method you need.

if (!isset($_GET['category'])) {
    // category isn't set
} elseif ($_GET['category'] === '0') {
    // category is set to 0
} else {
    // category is set to something other than 0
}

Note that I have compared for exact equality to the string '0', because GET and POST variables are always strings (or occasionally arrays) and never numbers when PHP first receives them.

Answer 2

There is the filter_input-function for such cases.

Answer 3

Try this:

if (!isset($_GET['category'])) { // if variable not specified
}
elseif ($_GET['category'] == 0) { // variable is specified and zero
}
else { // variable is specified and not zero
}

Answer 4

Make sure the name attribute of the element that is doing get on the previous page is set, preferably to the same as its id. Then:

$category='';
if ( !isset( $_GET['category'] ) ){
    //1
} else {
    $category=$_GET['category'];
    //3
  if($category==0){
    //2
   }
}

Answer 5

if (!isset($_GET['category']))
{
    1. Do something if $_GET['category'] does not exist at all
}
elseif ($_GET['category'] == 0)
{
    2. Do something if $_GET['category'] == 0
}
elseif (isset($_GET['category']) && ($_GET['category'] != 0)
{
    3. Do something if $_GET['category'] == something other than "does not exist" and 0.
}

My brackets might be slightly out somewhere but hopefully that should help you out.

Answer 6

<?php

$bad_values = array(null, '', 'dirty word');

if(isset($_GET['xd']))
{
    if(in_array($_GET['xd'], $bad_values, true))
    {
        // bad, it was null, empty or something else you think is not ok 
    }
    else
    {
        // it's fine, now check whether you got the zero. do a string comparison 

        if($_GET['xd'] == '0')
        {
            // you got the zero, yell at the user
        }
        else
        {
            // you got something else, it might be fine, it might be spoofed. use referential integrity to enforce data integrity in your db
        }
    }
}
else
{
    // it wasn't even sent in the request, that falls under 1)
}