exercism-php/reverse-string/ReverseString.php

<?php

/*
 * By adding type hints and enabling strict type checking, code can become
 * easier to read, self-documenting and reduce the number of potential bugs.
 * By default, type declarations are non-strict, which means they will attempt
 * to change the original type to match the type specified by the
 * type-declaration.
 *
 * In other words, if you pass a string to a function requiring a float,
 * it will attempt to convert the string value to a float.
 *
 * To enable strict mode, a single declare directive must be placed at the top
 * of the file.
 * This means that the strictness of typing is configured on a per-file basis.
 * This directive not only affects the type declarations of parameters, but also
 * a function's return type.
 *
 * For more info review the Concept on strict type checking in the PHP track
 * <link>.
 *
 * To disable strict typing, comment out the directive below.
 */

declare(strict_types=1);

/**
 * strrev() does not support multibyte inputs, so we need to use multibyte-aware functions.
 */
function reverseString(string $text): string
{
  $max = mb_strlen($text);
  $res = "";
  for ($i = 0; $i < $max; $i++) {
    $res .= mb_substr($text, $max-$i-1, 1);
  }
  return $res;
}