How do I reverse a string in PHP?

Answer 1

There's strrev() to do this.

if you want to built it on your own (for learning?): your problem is that you're starting with your index one too high - a string of legth 25 is indexed from 0 to 24, so your loop hast to look like this:

for ($i = $len - 1; $i >=0;$i--)
{
  echo $stringExp[$i];
}

Answer 2

It is extremely simple, so here it is in operation:
<?php $data = "Hello"; echo strrev($data); //olleH ?>