PHP Notice: Undefined index although using try\\ca

问题:

This is my try/catch block in PHP:

try
{
    $api = new api($_GET["id"]);
    echo $api -> processRequest();
} catch (Exception $e) {
    $error = array("error" => $e->getMessage());
    echo json_encode($error);
}

When there is nothing in the $_GET["id"], I still get the notice error. How can I avoid getting this error?

回答1:

use isset function to check if the variable is set or not:

if( isset($_GET['id'])){
    $api = new api($_GET["id"]);
    echo $api -> processRequest();
}

回答2:

If you want a fast and "dirty" solution, you can use

$api = new api(@$_GET["id"]);

Edit:

Since PHP 7.0 there is a much better and accepted solution: using the null coalescing operator (??). With it you can shorten your code to

$api = new api($_GET["id"] ?? null);

and you don't get a notice because you defined what should happen in the case the variable is not defined.

回答3:

If the absence of id means nothing should then be processed, then you should be testing for the absence of the id, and managing the failure gracefully.

if(!isset($_GET['id'] || empty($_GET['id']){
// abort early
}

THEN go on and do you try/catch.

Unless of course you were to add some smartness to api() so that is responded with a default id, that you'd declare in the function

function api($id = 1) {}

So, it "all depends", but try and fail early if you can.

回答4:

Try checking if the $_GET was set

try
{
    if(isset($_GET["id"]))
    {
      $api = new api($_GET["id"]);
      echo $api -> processRequest();
    }
} catch (Exception $e) {
    $error = array("error" => $e->getMessage());
    echo json_encode($error);
}