PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

150 Chapter 5 Reusing Code and Writing Functions
If you want the same data displayed in a more spread-out style, you could call the new
function as follows:
create_table2($my_array, 3, 8, 8);
Optional values do not all need to be provided; you can provide some and ignore some.
Parameters are assigned from left to right.
Keep in mind that you cannot leave out one optional parameter but include a later
listed one. In this example, if you want to pass a value for cellspacing, you will have to
pass one for cellpadding as well.This is a common cause of programming errors. It is
also the reason that optional parameters are specified last in any list of parameters.
The function call
create_table2($my_array, 3);
is perfectly legal and results in $border being set to 3 and $cellpadding and
$cellspacing being set to their defaults.
You also can declare functions that accept a variable number of parameters.You can
find out how many parameters have been passed and what their values are with the aid
of three helper functions: func_num_args(), func_get_arg(), and func_get_args().
For example, consider this function:
function var_args() {
echo "Number of parameters:";
echo func_num_args();
echo "";
$args = func_get_args();
foreach ($args as $arg) {
echo $arg."";
}
}
This function reports the number of parameters passed to it and prints out each of them.
The func_num_args() function returns the number of arguments passed in.The
func_get_args() function returns an array of the arguments. Alternatively, you can
access the arguments one at a time using the func_get_arg() function, passing it the
argument number you want to access. (Arguments are numbered starting from zero.)
Understanding Scope
You might have noticed that when we needed to use variables inside a required or
included file, we simply declared them in the script before the require() or include()
statement.When using a function, we explicitly passed those variables into the function
partly because no mechanism exists for explicitly passing variables to a required or
included file and partly because variable scope behaves differently for functions.