Take, as an example, this abstract class from a project I am working on. (minus all the really interesting bits).
abstract class col_meta extends meta {
protected $col_obj;
public function inject_object(&$obj);
public function &get_object(){
return $this->col_obj;
}
}
I understand that the inject_object method receives $obj as a reference but if I want the class to assign it to a protected variable do I need to assign by reference again?
like this:
class foo extends col_meta {
public function inject_object(&$obj){
$this->col_obj = &$obj;
}
}
Or, having only been given a reference, do I need to simply copy the reference into the protected variable?
class bar extends col_meta {
public function inject_object(&$obj){
$this->col_obj = $obj;
}
}
I've been tying my mind up in knots trying to work this out as they both seem right.
By definition, by reference is "by reference"; meaning that if the value is changed in the function, it's changed in the calling script.
However - because it provides better performance - if you pass "by value", PHP still passes the reference to the function, but creates a copy (by value) if you change the value in the function.
Note that objects are always effectively "pass by reference", because your object variable is actually a pointer to the object, so any changes to an object inside the function will be reflected outside the function as well.
Don't pass by reference unless you explicitly want a variable changed inside the function to be changed outside the function as well.
If you want a "copy" of the object inside you class, rather than the reference; then use clone to create a copy.