如何正确定义PHP类中的数组以防止未定义的索引错误？

I'm trying a little PHP and am trying to understand why I keep getting an undefined index error for the following:

class foo {
  public static some_dict;

  public function fillSomeDict() {
    self::some_dict = array(1=>"foo",2=>"baz",4=>"cous");
  }

  public function dump() {
     $err = error_get_last();
     $type = $err["type"];

     echo self::some_dict[$type];

  }

  public function setup() {
    register_shutdown_function(array($this, "dump"));
  }
}

$x = new foo();
$x->fillSomeDict();

My problem ist, I'm always getting ´undefined index´ errors on this line some_dict[$type]. I have already tried to populate the array on __construct, through the parent call (example here), but it still does not work...

Question: How do I correctly reference elements of this array in PHP? How do I set them correctly?

Thanks!

You should check whether $err is an array before access to it as an array.

And check whether do you have an element in self::$some_dict with index $err['type'] (i am doing this in 'echo')

    public function dump() {
        $err = error_get_last();
        if(!is_array($err)) {
            echo 'No errors!';
            return;
        }

        echo isset(self::$some_dict[$err["type"]]) ? self::$some_dict[$err["type"]] : 'No error with index "'.$err["type"].'"';
  }

You need to define your array when you initialize the variable.

So change

 public static $some_dict;

to

public static $some_dict = array(1=>"foo",2=>"baz",4=>"cous");

when you call it you need to use the $ and use isset

if(isset(self::$some_dict[$err["type"]])){ echo self::$some_dict[$err["type"]]; }