Correct PHP code to check if a variable exists

Question

This code is part of a websocket server:

$msgArray = json_decode($msg);
if ($msgArray->sciID) {
  echo "Has sciID";
}

It will either be receiving a json string like {"sciID":67812343} or a completely different json string with no sciID such as {"something":"else"}.

When the server receives the later, it echos out: Notice: Undefined property: stdClass::$sciID in /path/to/file.php on line 10

What is the correct code to check if $msgArray->sciID exists?

Answer 1

Use isset as a general purpose check (you could also use property_exists since you're dealing with an object):

if (isset($msgArray->sciID)) {
    echo "Has sciID";
}

Answer 2

property_exists()?

Answer 3

In case isset() or property_exists() doesn't work, we can use array_key_exists()

if (array_key_exists("key", $array)) {
    echo "Has key";
}