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));

Answer 2

Here it is PHP7 version of this:

echo "\u{202E}abcdefg"; // outs: gfedcba

Answer 3

//Reverse String word by word
$str = "Reverse string word by word";
$i = 0;
while ($d = $str[$i]) {
    if($d == " ") {
        $out = " ".$temp.$out;
        $temp = "";
    }
    else
        $temp .= $d;

    $i++;
}
echo $temp.$out;

Answer 4

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

Answer 5

   <?php
     $value = 'abcdefg';
     $length_value = strlen($value);
     for($i = $length_value-1; $i >=0 ;$i--){    
       echo $value[$i];
     }
   ?>