没有数据发送时如何处理GET变量

Question

On my webpage, I have 2 options, to create a new list or to edit an existing list.

If the user wishes to create a new list, a new page with a textarea comes up.

If the user wishes to edit an existing list, the lists are displayed and the user can select a list. Upon selection of the list, the user is redirected to the new list page with the text area contents already filled in.

I have this if statement in the new list page to accept input from the edit-list page:

$items = $_GET['items'];
if ($items){
    //get the stuff from the db and populate the text area
}
else {
    //a new empty text area
}

The issue is that when I try reaching this page directly from the 'create new list' option, I get an error stating that items is an undefined variable. This makes sense as the original page is not sending any data so there is nothing to get.

How can I work around this? I can set the original page up to send a null value for items but I want to refrain from changing the original page. Is there an option to check from where the request is coming from, or an option to activate a variable only if it can be received (usable by the GET feature)?

Answer 1

Use isset() :

isset — Determine if a variable is set and is not NULL

if (isset($_GET['items'])){
    //get the stuff from the db and populate the text area
    $items = $_GET['items'];
}

---

@Eugen suggestion(check before assigning the variable:

$items = isset($_GET['items']) ? $_GET['items'] : null; 
if($items) { // bla bla }

Answer 2

Firstly you must write/check

print_r($_GET)

if you want only check it you can use

if(isset($_GET["items"]){
      //it have a value
}

Plus:If a variable has been unset with unset(), it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\\0") is not equivalent to the PHP NULL constant.

Answer 3

You want this. You need to check if $_GET['items'] is set, and then you can set $items to the result.

if (isset($_GET['items']) && $items = $_GET['items']){
    //get the stuff from the db and populate the text area
}
else {
    //a new empty text area
}