string_task.php

<?php
// 7 kyu - String Task
// Petya started to attend programming lessons. On the first lesson his task was to write a simple program. The program was supposed to do the following: in the given string, consisting of uppercase and lowercase Latin letters, it:
//
// deletes all the vowels,
// inserts a character "." before each consonant,
// replaces all uppercase consonants with corresponding lowercase ones.
//  Vowels are letters "A", "O", "Y", "E", "U", "I", and the rest are consonants. The program's input is exactly one string, it should return the output as a single string, resulting after the program's processing the initial string.
//
// Input:
//  The first argument represents input string of Petya's program. This string only consists of uppercase and lowercase Latin letters.
//
// Output:
//  Return the resulting string.
//
// Examples:
//
// ('tour')      =>  '.t.r'
// ('Codewars')  =>  '.c.d.w.r.s'
// ('aBAcAba')   =>  '.b.c.b'

function string_task(string $s): string {
  return preg_replace_callback( '/./', function ($l) {
      return '.' . $l[0];
  }, preg_replace('/[aeiouy]/i', '', strtolower($s)));
}

// Alternative Solution:
// function string_task(string $s): string {
//   return preg_replace('/./', ".$0", preg_replace('/[aeiouy]/', '', strtolower($s)));
// }

// function string_task(string $s): string {
//      return preg_replace(['/[aiyeuo]/', '/([^aiyeuo])/'], ['', '.$1'], strtolower($s));
// }


?>