<?php
$patterns = ["are", "finite", "get", "er"];
$string = "You are definitely getting better today www.get.com";
$alternations = ''.implode('|', $patterns);
$re = '(?<=\s)(?:are|finite|get|er)(?=\s)';
$string = preg_replace('#'.$re.'#', '', $string);
$string = preg_replace('#\h{2,}#', ' ', $string);
echo $string;