Question

In C++ when you want a function to be able to read from an object, but not modify it, you pass a const reference to the function. What is the equivalent way of doing this in php?

I know objects in php5 are passed by reference by default, but for readability I think I will continue to use the ampersand before the variable name, like this:

function foo(&$obj)
{

}

Answer 1

If you want to pass an object but not by reference you can clone the object beforehand.

<?php
function changeObject($obj) {
  $obj->name = 'Mike';
}

$obj = new StdClass;
$obj->name = 'John';

changeObject(clone $obj);
echo $obj->name; // John

changeObject($obj);
echo $obj->name; // Mike

I know objects in php5 are passed by reference by default, but for readability I think I will continue to use the ampersand before the variable name

That’s your call but I find that would simply make it read more like C++. Alternativly, you can show that an object is being passed in by using type-hinting in your function definition:

function foo(StdClass $obj)
{

}

Once it’s clear that $obj is an object it can be assumed that it’s being passed by reference.