<?php

$a = [
    74 => 'http://w...content-available-to-author-only...k.ru'
    ,75 => 'http://w...content-available-to-author-only...k.ru'
    ,76 => 'http://w...content-available-to-author-only...k.ru'
    ,77 => 'http://w...content-available-to-author-only...k.ru'
    ,78 => 'http://w...content-available-to-author-only...k.ru'
    ,104 => 'http://w...content-available-to-author-only...k.com'
    ,105 => 'http://w...content-available-to-author-only...k.info'
    ,106 => 'http://w...content-available-to-author-only...k.info'
    ,107 => 'http://w...content-available-to-author-only...k.net'
    ,108 => 'http://w...content-available-to-author-only...k.net'
    ,109 => 'http://w...content-available-to-author-only...k.org'
    ,110 => 'http://w...content-available-to-author-only...k.org'
    ,111 => 'http://w...content-available-to-author-only...k.ru'
    ,112 => 'http://w...content-available-to-author-only...k.ru'
];

print_r (array_unique (array_map(function($url){
  $url = preg_replace ('|(.+\.)(.+)\.(.+)|', '$2.ru', $url);
  $url = str_replace ('-', '', $url);
  return $url;
  
}, $a)));