exercism-php/acronym/Acronym.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);

function acronym(string $text): string
{
  $parts = array_filter(mb_split("[^\w']", $text));
  if (count($parts) <= 1) {
    return "";
  }
  $parts2 = [];
  foreach ($parts as $part) {
    $first = mb_substr($part, 0, 1);
    if (mb_strlen($part) == 1) {
      $parts2[] = $first;
      continue;
    }
    $first = mb_strtoupper($first);
    $part = $first . mb_substr($part, 1);

    $part = mb_ereg_replace("[a-z]", " ", $part);
    $subs = array_filter(mb_split("[\s]", $part));
    foreach ($subs as $sub) {
      $parts2[] = $sub;
    }
  }
  $reduced = array_reduce($parts2, function($accu, $v) { return $accu . mb_substr($v, 0, 1); } );
  return mb_strtoupper($reduced);
}