Weird logic error

[eluser]diego.greyrobot[/eluser]
I default $id to false so that i can call that function with or without arguments. Help me to understand this correctly, if i use a default in the arg declaration AND i pass a value in $id in that function, the if else block will use both values?

if i delete the default value for $id and later call this function without arguments, will there be a problem?