PHP中的可选函数输入

Question

I notice that in some PHP built in functions such as str_replace there are optional input variables. Can I have have optional input variables in my own functions? If so, how?

Thanks, Brian

Answer 1

The first way is to use default values for some arguments:

function doStuff($required, $optional = '', $optional2 = '') {
  ...
}

Now you just include a default value and then someone can do:

doStuff('foo');
doStuff('foo', 1);
doStuff('foo', 2, 3);

You need to choose an appropriate default value if the field isn't specified or to indicate that no value was set. Typical examples are '', 0, false, null or array().

Or you don't need to specify them at all with func_get_args():

function doStuff() {
  print_r(func_get_args());
}

func_get_args() can be used with explicit arguments (the first example) as well.