如何使用Preg_match数组(多键)?

例如,我有这几个关键字

$word = "word1,word2,word3";

and substract/explode that using $keyword = explode(",", trim($word)); then ill get these $keyword[0] $keyword[1] and $keyword[2]

现在,如何使用preg_match匹配这些关键字?

$others = "this is example where there is word1"; 

if(preg_match('/($keyword[0]|$keyword[1]|$keyword[2])/i', $others)){
echo "matched";
}

the problem is, if there is only 2 words, it will matched all the words in $others.

还有其他更合适或更简单有效的方法吗?