PHP - defining classes inside a function

Question

Is this a bad practice?

like:

function boo(){
  require_once("class.moo.php");
}
...

?

Answer 1

Yes it is bad practice; no it's not.

You're likely going to get both answers, and here's why:

If you use __autoload (or equivalent), calling:

function someFunc()
{
  $n = new UndefinedClassName();
}

is equivalent to:

function someFunc()
{
  include('path/to/UndefinedClassName.php');
  //may be require_once, include_once, include, or require
  //depending on how autoload is written
  $n = new UndefinedClassName();
}

But you'll get better performance out of your code if you avoid using __autoload. And to maintain your code, it's better to put all your includes at the top of the script like you would for import statements in other languages.

include('path/to/UndefinedClassName.php');
...code...
function someFunc()
{
  $n = new UndefinedClassName();
}

I would suggest consistency. If you consistently call the include in the functions, you shouldn't have too many issues, but I would choose imports at the beginnings of files, or as autoloads.

Answer 2

I would avoid it.

It is not what another developer would expect, and, as such, would reduce the maintainability of your code.

Answer 3

This is how class loaders work. This is not necessarily bad practice.

Depends on what the function does and why you are doing this. Using autoloading may be more appropriate.