Question

How do you validate/manage your PHP method arguments and why do you do it this way?

Answer 1

Well, assuming that you’re talking about type-checking method arguments, it depends:

1. If it’s expecting an object, I use type-hinting with an interface:

   public function foo(iBar $bar)
   

2. If it’s expecting an array only, I use type-hinting with the array keyword.

   public function foo(array $bar)
   

3. If it’s expecting a string, int, bool or float, I cast it:

   public function foo($bar) {
       $bar = (int) $bar;
   }
   

4. If it’s expecting mixed, I just check in a cascade:

   public function foo($bar) {
       if (is_string($bar)) {
           //handle string case
       } elseif (is_array($bar)) {
           //...
       } else {
           throw new InvalidArgumentException("invalid type");
       }
   }
   

5. Lastly, if it’s expecting an iterable type, I don’t use type-hinting. I check if it’s an array first, then re-load the iterator:

   public function foo($bar) {
       if (is_array($bar)) {
           $bar = new ArrayIterator($bar);
       }
       if (!$bar instanceof Traversable) {
           throw new InvalidArgumentException("Not an Iterator");
       }
   }
   

6. If it’s expecting a filename or directory, just confirm it with is_file:

   public function foo($bar) {
       if (!is_file($bar)) {
           throw new InvalidArgumentException("File doesn't exist");
       }
   }
   

I think that handles most of the cases. If you think of any others, I’ll gladly try to answer them…