Transfer of an instanced object into a class - php

Question

I was wondering what is the best way to transfer an instanced object into another class for local usage. I am also curious if this makes a differences with regards to memory usage.
I figured, there are mainly two ways:
1.) Transfer instanced objects via referencing to $GLOBALS:
class UserLogHandler {
public function __construct() {
$this->DB = $GLOBALS['DB'];
$this->Security = $GLOBALS['Security'];
}
public function doSomeWork() {
$this->DB->someMethod;
}
}
or
2.) Transfer via handover:
class UserLogHandler($DB,$Security) {
public function doSomeWork() {
$DB->someMethod;
}
}
It seems to me, that option 2 might be better suited for a complicated environment, although I find option 1 more appealing. Anyhow I would prefer a technical and/or logical explanation why to use one option over the other. If there is another, better option please let me know as well.
Thanks in advance and best wishes,
Thomas

Answer 1

This is indeed a good question. I will say it depends upon your need. Lets analyze both your options one by one.
Before starting, keep in mind that your object should always a complete object. It should not have a incomplete state. You can refer to this article for more understanding https://matthiasnoback.nl/2018/07/objects-should-be-constructed-in-one-go/
1.) Transfer instanced objects via referencing to $GLOBALS:
You must never use such methods as they are confusing. $GLOBALS lacks to tell you where and how a particular variable was created so You can't never be sure if this variable exist or what it holds. I will suggest you to use dependency injection for it
use DB;
use Security;
class UserLogHandler
{
public function __construct(DB $DB, Security $Security)
{
$this->DB = $DB;
$this->Security = $Security;
}
public function doSomeWork()
{
$this->DB->someMethod;
}
}
See how you can now be sure that from where $DB and $Security where injected and what they hold. You can even enforce type of variable using type indication like Security $Security.
This method comes handy when your class is heavy dependent on a particular variable. e.g. A model class will always need DB adapter or a PDF generator library will need PDF class essentially.
2.) Transfer via handover
This works as you expected but I think you made mistake while defining it. You need to write it like following.
class UserLogHandler
{
public function doSomeWork($DB, $Security)
{
$DB->someMethod;
}
}
This method comes handy when you need a particular variable in a particular function only. Example for it, will be like we need to get records from a model for some particular condition. So we can pass value in function and get results according to value.
use DB;
use Security;
class UserLogHandler
{
public function __construct(DB $DB, $Security)
{
$this->DB = $DB;
$this->Security = $Security;
}
public function doSomeWork($value)
{
if ($value = 'something') {
$this->DB->someMethod;
}
}
}
As you can see that both methods can be used in conjugation. It only depends what is your requirement