How Can I Generate All Unique Combinations of a Specific Length from a PHP Array?

PHP Array Combinations

In PHP, creating combinations of elements from an array is a common task. This article explores a solution to generate combinations of specific length from a given array, ensuring that the order of elements is disregarded.

To tackle this problem, an iterative approach is employed, implemented through the Combinations class. This class serves as an iterator, allowing for efficient traversal and retrieval of combinations.

The __construct method initializes the class by accepting an array or string s and the desired combination length k. It initializes internal variables and sets the initial position to zero.

The _next method is responsible for advancing to the next combination. It iterates through the elements in reverse order, incrementing the count and updating the combination accordingly.

The key, current, next, rewind, and valid methods fulfill the Iterator interface requirements, enabling seamless iteration over the combinations.

An example usage is provided, demonstrating the creation of a Combinations object from an array of numbers:

$array = [1,2,3,4,5,6,7];
$combinations = new Combinations($array, 5);

Iterating over the $combinations object will yield each unique combination as a string or an array, depending on the input type:

foreach($combinations as $combination) {
    echo $combination . ' ';
}

Output:

12345 12346 12347 12356 12357 12367 12456 12457 12467 12567 13456 13457 13467 13567 14567 23456 23457 23467 23567 24567 34567

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