Price formatter

gistfile1.php

$string = '1000000000';

$array = preg_split('/(?<!^)(?!$)/u', $string);
$array = array_chunk(array_reverse($array), 3);

foreach($array as &$a){
    $a = implode("", $a);
}

$result = implode(" ", array_reverse($array));

return $result;