Im seeking a solution to check for duplicate entries with an other sequence

Hello,

I have a question currently i'm programming a function to remove duplicates
from an array of sentences.
The computer must classify sentences with exactly the same words in it, but
with a different sequence as a duplicate.

The array that i use as a feed is as following:
$sentences[] = "this is a example sentence";
$sentences[] = "a this is example sentence";
$sentences[] = "example this is a sentence";
$sentences[] = "this is a example sentence for a function";

I want the computer to keep only two records of the sentence array in this
case (0|1|2) and 3

I made the script as following:

function($sentences) {

    foreach($sentences as $sentence) {
        $words = explode(" ",$sentence);
        $sentenceArray[] = $words;
    }

    foreach(sentenceArray as $sentence) {
        // Here i want the same words are in other sentences
    }

}

My question is how could i check the $sentence array if there are records in
it with exactly the same words
as my feed?