Reverse string without strrev

Question

Some time ago during a job interview I got the task to reverse a string in PHP without using strrev.

My first solution was something like this:

Answer 1

Try this:

$s = 'abcdefg';

for ($i = strlen($s)-1; $i>=0; $i--) {
       $s .= $s[$i];
       $s[$i] = NULL;
 }
var_dump(trim($s));