注意：未定义的偏移量：0 - 用于错误消息

Question

I'm trying to display an error message for a required field but it is just redirecting to the page it should go to if something is entered (I'm leaving it empty)

$required_fields = array('NativeLanguage');
    foreach ($required_fields as $val) {
        while (is_array($val))
            $val = reset($val);
    if (!empty($_POST[$val])) {
        $val = trim($_POST[$val]);
    }
    else {
        $err[] = "ERROR - $val is required";
    }
    }

Answer 1

The array vales are not set, so when PHP is trying to access the value of those array keys it encounters an undefined offset.

$new_array = array('1','2','3');//If I have an array
//We can now access:
$new_array[0];
$new_Array[1];
$new_array[2];
//If we try and access
$new_Array[3];

we will get the same error-->error->notice undefined offset