title: Efficient replacement for substr?
body: <p>Let's say we have a very large string <code>$str</code>, and we need to pass a significant portion of it (let's say the whole string, but without the first 3 bytes) to a function.  The way to do it with <code>substr</code>:</p>
  
  <pre><code>consumer_function(substr($str, 3));
  </code></pre>
  
  <p>doesn't seem efficient, because <code>substr</code> appears to copy characters from the initial string into a new string before returning the result. Is there any way we could pass a large portion of that string to a function without excessive copying? We can't change the code of that function.</p>