<?php

$re = '/^(?=.*\bWord1\b)(?=.*\bWord2\b)(?=.*\bWord3\b)/'; 
$str = "Word4 Word2 Word1 Word3 Word5 Word7"; 

$myPregMatch = (preg_match($re, $str));
 if ($myPregMatch){
    echo  "FOUND !!!";
 }