func_get_arg(),func_get_args()和func_num_args()的用法

function foo()
{
    $numargs = func_num_args();
    echo "Number of arguments: $numargs<br />\n";
    if ($numargs >= 2) {
        echo "Second argument is: " . func_get_arg(1) . "<br />\n";
    }
    $arg_list = func_get_args();
    for ($i = 0; $i < $numargs; $i++) {
        echo "Argument $i is: " . $arg_list[$i] . "<br />\n";
    }
}
foo(1, 2, 3);

//输出：
//Number of arguments: 3
//Second argument is: 2
//Argument 0 is: 1
//Argument 1 is: 2
//Argument 2 is: 3