PHP：在多维数组中枚举所有可能的组合

Question

I have an array:

$array = array ( 'tag1' => array ('apple', 'orange','cherries') ,
                  'tag2' => array ('delicious' , 'yummy', 'tasty', 'good')
                  'tag3' => array ('green', 'red', 'orange')
                );

I would like to produce another array with every possible combination regardless of order but including every combination (power set). For example:

$result = array (
             array(),
             array('tag1' => 'apple'),
             array('tag1' => 'orange'),
             array('tag1' => 'cherries'),
             array('tag2' => 'delicious'),
             array('tag2' => 'yummy'),
             array('tag2' => 'tasty'),
             array('tag2' => 'good'),
             array('tag3' => 'green'),
             array('tag3' => 'red'),
             array('tag3' => 'orange'),
             array('tag1' => 'apple', 'tag2' => 'delicious'),
             array('tag1' => 'apple', 'tag2' => 'yummy'),
             array('tag1' => 'apple', 'tag2' => 'tasty'),
             array('tag1' => 'apple', 'tag2' => 'good'),
             array('tag1' => 'apple', 'tag3' => 'green'),
             array('tag1' => 'apple', 'tag3' => 'red'),
             array('tag1' => 'apple', 'tag3' => 'orange'),
             array('tag1' => 'apple', 'tag2' => 'delicious', 'tag3' => 'green'),
             array('tag1' => 'apple', 'tag2' => 'delicious', 'tag3' => 'red'),
             array('tag1' => 'apple', 'tag2' => 'delicious', 'tag3' => 'orange'),
             ..
);

Does anyone know what function can be written to achieve this? I believe it might have to be a recursive function, but I haven't been able to come up with anything that fits all my requirements so far.

Answer 1

function power_set($array) {
    $results = [[]];

    foreach($array as $tag => $features) {
        foreach ($results as $combination) {
            foreach ($features as $feature) {
                array_push($results, array_merge([$tag => $feature], $combination));
            }
        }
    }

    return $results;
}

$array = array(
    'tag1' => array ('apple', 'orange','cherries') ,
    'tag2' => array ('delicious' , 'yummy', 'tasty', 'good'),
    'tag3' => array ('green', 'red', 'orange')
);

print_r(power_set($array))