<?php

$m3uData = file_get_contents("http://site.com/list.m3u"); //удаленный m3u
$localData = file_get_contents("local.txt"); //локальный файл

$regex = "([A-Z\d\.-]{2,})\.([A-Z]{2,})(:\d{2,4})?/i";

$matches = array();
$localMatches =

if(preg_match($regex,$m3uData,$matches) && preg_match($regex,$m3uData,$localMatches) ){
  $localData = str_replace($localMatches[0],$matches[0],$localData);
  file_put_contents($localData,"local.txt");
}


?>