If you append
to a string value, it is converted to an array value and then
appended to. You can explicitly pass name/value pairs, or associative
arrays containing the name/value pairs. If you pass the optional third
parameter of true, the value will be merged with the current array
instead of appended.
Technical Note:
The merge parameter respects array keys, so if
you merge two numerically indexed arrays, they may overwrite each other
or result in non-sequential keys. This is unlike the
array_merge() function
of PHP which wipes out numerical keys and renumbers them.