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

you could use substr with negative start.

Theory & Explanation

you can start with for loop with counter from 1 to length of string, and call substr inside iteration with counter * -1 (which will convert the counter into negative value) and length of 1.

So for the first time counter would be 1 and by multiplying with -1 will turn it to -1

Hence substr('abcdefg', -1, 1); will get you g
and next iteration substr('abcdefg', -2, 1); will get you f
and                       substr('abcdefg', -3, 1); will get you e
and so on ...

Code

$str = 'abcdefghijklmnopqrstuvwxyz';
for($i=1; $i <= strlen($str); $i++) {
    echo substr($str, $i*-1, 1);
}

In Action: https://eval.in/583208