Description:
------------
Usually when you don't want to pass an optional argument you pass null. That does not only feel natural for me I hope. But not with substr - when you pass null it is the same as when you pass 0. It is clearly described in the documentation as well.

This looks like no problem for the most of the users. Obviously just don't pass it. But no one knows what the developers out there might develop; maybe the third parameter comes from another call and you have to write an exception for substr:

<?php

if ($length === null) 
  $sub = substr($string, $offset);
else
  $sub = substr($string, $offset, $length);

I'm not sure is it really intended to be that way or are there only historical reasons?

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From manual page: https://php.net/function.substr
---


Test script:
---------------
<?php

$string = 'lorem ipsum';
$passNull = substr($string, 6, null);

var_dump($passNull);

Expected result:
----------------
string(5) "ipsum"

Actual result:
--------------
string(0) ""