Get all ordered, contiguous combinations of an array's elements

Question

I want to get all possible phrases (which actually exist) in a sentence as

$str = 'word1 word2 word3 word4';

$output = array ('word1 word2 word3', 'word1 word2', 
                 'word2 word3 word4', 'word3 word4', 'word2 word3');

To do so, I create an array of words as,

$words = explode(' ', $str);

There are several questions here explaining how to build all combinations of the elements of an array, but how can I make all the combinations while preserving the original order?

How can I make the array of $output out of $words?

https://stackoverflow.com/questions/19067556/php-algorithm-to-generate-all-combinations-of-a-specific-size-from-a-single-set# — mayur saptal, Nov 04 '18 at 18:53
@mayursaptal that's the opposite of what I want by disregarding the order for a specific size. I want different sizes of the same order. — Googlebot, Nov 04 '18 at 18:56
Why isn't `word1 word3` a possible combination in expected output ? — Madhur Bhaiya, Nov 04 '18 at 18:57
@MadhurBhaiya Because it is not in the sequential order. I want to get all phrases (substrings) in the sentence (string). — Googlebot, Nov 04 '18 at 19:00
Why isn't `word1 word2 word3 word4` also one of the expected output ? — Madhur Bhaiya, Nov 04 '18 at 19:01
@MadhurBhaiya yes it can be, a string is a substring of itself too. — Googlebot, Nov 04 '18 at 19:03
@Googlebot Hint: two nested loops; one running from start to end; another end to start; also use `array_slice()`. — Madhur Bhaiya, Nov 04 '18 at 19:06
@MadhurBhaiya I thought about that but then cannot get the middle substrings like `word2 word3`. — Googlebot, Nov 04 '18 at 19:08

Madhur Bhaiya · Accepted Answer · 2018-11-04T19:58:35.370

We can use array_slice() function to take a chunk out of the input array. It will also ensure that the order is maintained, as well as the combinations are of the successive values (as per the original array).
Now, we need to use two nested loops, to determine $offset, and $length for the chunk.
$offset value will basically loop from the beginning to end; $length will initially be count of remaining values from the offset, and it will be decrementing upto 2 (we don't want single values as combinations).

Try the following (Rextester DEMO):

$str = 'word1 word2 word3 word4';
$words = explode(' ', $str);

$combinations = array();

// offset from start to end of the words
for($offset = 0; $offset < count($words); $offset++) {

    // length from available remaining words to 2
    for ($length = count($words) - $offset; $length > 1; $length--) {

        // get the array chunk
        $combinations[] = array_slice($words, $offset, $length);
    }
}

// test output
print_r($combinations);

Output:

Array
(
    [0] => Array
        (
            [0] => word1
            [1] => word2
            [2] => word3
            [3] => word4
        )

    [1] => Array
        (
            [0] => word1
            [1] => word2
            [2] => word3
        )

    [2] => Array
        (
            [0] => word1
            [1] => word2
        )

    [3] => Array
        (
            [0] => word2
            [1] => word3
            [2] => word4
        )

    [4] => Array
        (
            [0] => word2
            [1] => word3
        )

    [5] => Array
        (
            [0] => word3
            [1] => word4
        )

)

Get all ordered, contiguous combinations of an array's elements

1 Answers1