PHP is it OK to try access an associative array if you are unsure the key exists?
<p>Is it OK to rely on PHP's behaviour if a key is not in the array? Which is:</p>

<blockquote>
  <p>Attempting to access an array key which has not been defined is the same as accessing any other undefined variable: an E_NOTICE-level error message will be issued, and the result will be NULL.</p>
</blockquote>

<p>For instance if I do not know $_POST contains certain keys is it OK to just try? I want the result to be null anyway. Or is there a better way?</p>
