Better way to check variable for null or empty string?

Question

Since PHP is a dynamic language what's the best way of checking to see if a provided field is empty?

I want to ensure that:

1. null is considered an empty string
2. a white space only string is considered empty
3. that "0" is not considered empty

This is what I've got so far:

$question = trim($_POST['question']);

if ("" === "$question") {
    // Handle error here
}

There must be a simpler way of doing this?

Answer 1

Function for basic field validation (present and neither empty nor only white space

function IsNullOrEmptyString(string|null $str){
    return $str === null || trim($str) === '';
}