如何判断PHP方法/函数中是否设置了可选参数？

Question

Assume I have a method/function with the following signature:

foo($bar = 0)

Inside foo, how do I tell if $bar was set or not? isset will alway return a TRUE since $bar is assigned 0 in the event nothing is passed to foo.

Checking for 0 is not an option. I need to know the difference between the parameter explicitly being set to 0 or defaulting to 0.

Answer 1

Simply use func_num_args() to specifically check for how many arguments were passed in.

<?php
function foo($bar = 0)
{
    echo "
Number of arguments: " . func_num_args();
}

  // Outputs "Number of arguments: 1"
foo(0);

  // Outputs "Number of arguments: 0"
foo();
?>    

Live example