public static function flatten(array $arr)
    {
        $flat = [];
        foreach ($arr as $v) {
            if (is_array($v)) {
                $flat = array_merge($flat, self::flatten($v));
            } else {
                $flat[] = $v;
            }
        }
        return $flat;
    }
public static function flatten(array $arr)
    {
        $flat = [];
        foreach ($arr as $v) {
            if (is_array($v)) {
                $flat = array_merge($flat, self::flatten($v));
            } else {
                $flat[] = $v;
            }
        }
        return $flat;
    }
public static function flatten ( array $ arr ) { $ flat = [ ] ; foreach ( $ arr as $ v ) { if ( is_array ( $ v ) ) { $ flat = array_merge ( $ flat , self :: flatten ( $ v ) ) ; } else { $ flat [ ] = $ v ; } } return $ flat ; }
Flattens an array.
Flattens an array .