How to extract substring by start-index and end-index?

Question

$str = \'HelloWorld\';
$sub = substr($str, 3, 5);
echo $sub; // prints \"loWor\"

I know that substr() takes the first parameter, 2nd parameter is start

Answer 1

Not exactly...

If we have a start index as 0, and we want JUST the first char, it becomes difficult as this will not output what you want. So if your code is requiring an $end_index:

// We want just the first char only.
$start_index = 0;
$end_index = 0;
echo $str[$end_index - $start_index]; // One way... or...
if($end_index == 0) ++$end_index;
$sub = substr($str, $start_index, $end_index - $start_index);
echo $sub; // The other way.