Applies the user-defined function funcname to each
element of the input array. This function will recur
into deeper arrays. Typically, funcname takes on two
parameters. The input parameter's value being the first, and
the key/index second. If the optional userdata
parameter is supplied, it will be passed as the third parameter to
the callback funcname.
Returns TRUE on success or FALSE on failure.
Note:
If funcname needs to be working with the
actual values of the array, specify the first parameter of
funcname as a
reference. Then,
any changes made to those elements will be made in the
original array itself.