idArithmetic()
idArithmetic(string $action, array $options = array()) : mixed
Performs MIME ID "arithmetic".
Parameters
| string |
$action |
One of:
- ID_DOWN: ID of child. Note: ID_DOWN will first traverse to "$id.0"
if given an ID NOT of the form "$id.0". If given an ID of
the form "$id.0", ID_DOWN will traverse to "$id.1". This
behavior can be avoided if 'no_rfc822' option is set.
- ID_NEXT: ID of next sibling.
- ID_PREV: ID of previous sibling.
- ID_UP: ID of parent. Note: ID_UP will first traverse to "$id.0" if
given an ID NOT of the form "$id.0". If given an ID of the
form "$id.0", ID_UP will traverse to "$id". This behavior can
be avoided if 'no_rfc822' option is set.
|
| array |
$options |
Additional options:
- count: (integer) How many levels to traverse.
DEFAULT: 1
- no_rfc822: (boolean) Don't traverse RFC 822 sub-levels.
DEFAULT: false
|
Returns
mixed
— The resulting ID string, or null if that ID can not
exist.