Anonymous recursive function - Returns array with all possible combinations, (if array values are arrays, they will be transformed to objects)

combinations.php

<?php

$flatten = function ( & $combines) use ( & $flatten) {
    $current = pos($combines);
    $current = array_map(function ($v) {
        return is_array($v) ? (object) $v : $v;
    }, $current);

    if (!next($combines)) {
        $end = end($combines);
        $end = array_map(function ($v) {
            return is_array($v) ? (object) $v : $v;
        }, $end);
        return $end;
    }

    $temporary = $flatten($combines);
    $return = [];

    foreach ($current as $z => $v) {
        foreach ($temporary as $y => $t) {
            $return[] = is_array($t) ? array_merge([$z => $v], $t) : [$z => $v, $y => $t];
        }
    }

    next($combines);
    return $return;
};



/*
Usage:

$array = array(
    array('key_a' => '123'),
    array('key_b' => '456', 'key_c' => '789'),
    array('key_d' => '101112', 'key_f' => '131415'),
    array('key_g' => '161718')
);

var_dump($flatten($array));

Results:

array (size=4)
  0 => 
    array (size=4)
      'key_a' => string '123' (length=3)
      'key_b' => string '456' (length=3)
      'key_d' => string '101112' (length=6)
      'key_g' => string '161718' (length=6)
  1 => 
    array (size=4)
      'key_a' => string '123' (length=3)
      'key_b' => string '456' (length=3)
      'key_f' => string '131415' (length=6)
      'key_g' => string '161718' (length=6)
  2 => 
    array (size=4)
      'key_a' => string '123' (length=3)
      'key_c' => string '789' (length=3)
      'key_d' => string '101112' (length=6)
      'key_g' => string '161718' (length=6)
  3 => 
    array (size=4)
      'key_a' => string '123' (length=3)
      'key_c' => string '789' (length=3)
      'key_f' => string '131415' (length=6)
      'key_g' => string '161718' (length=6)

*/