function array_2d_to_1d ($input_array) {
    $output_array = array();

    for ($i = 0; $i < count($input_array); $i++) {
      for ($j = 0; $j < count($input_array[$i]); $j++) {
        $output_array[] = $input_array[$i][$j];
      }
    }

    return $output_array;
}

$array = array(array('green', 'yellow', 'orange'), array('blue', 'black', 'white'));
$newarray = array();
foreach (array_values($array) as $value){
   $newarray[] = $value;
}

function array_to1d($a) {
    $out = array();
    foreach ($a as $b) {
        foreach ($b as $c) {
            if (isset($c)) {
                $out[] = $c;
            }
        }
    }
    return $out;
}