<?php

$sentence = 'Im a professional.bowler';
var_dump(preg_match('/\bprofessional\b/i', $sentence)); //1
var_dump(preg_match('/\bprofessional\.bowler\b/i', $sentence)); //1

$wordList = array_flip(explode(' ', $sentence));
var_dump(isset($wordList['professional'])); //false
var_dump(isset($wordList['professional.bowler'])); //true