Define const as a variable - php

Question

I looked up a few solutions, but nothing that's able to solve it. I realize that constants are not supposed to be modifiable hence the whole point of the word "constant".
In this case I'm dealing with an API class that goes like this
class GetAdGroups {
const CAMPAIGN_ID = "";
I have to pass a value to CAMPAIGN_ID, but it can't be hard coded as a string.
So the following is not an option:
const CAMPAIGN_ID = 123;
I tried going with "define"
class GetAdGroups {
$my_var = 123;
define("CAMPAIGN_ID", "$my_var");
But it throws an error and when I define it outside the class scope, it also throws an error that the constant is not found.
Not sure what else to try. Pretty new to OOP and would appreciate your help

Answer 1

Check this what are new features in php 5.6
<?php
const ONE = 1;
const TWO = ONE * 2;
class C {
const THREE = TWO + 1;
const ONE_THIRD = ONE / self::THREE;
const SENTENCE = 'The value of THREE is '.self::THREE;
public function f($a = ONE + self::THREE) {
return $a;
}
}
echo (new C)->f()."\n";
echo C::SENTENCE;
?>
this may help you. You can use expression as constant value here.
Note:-
It is now possible to provide a scalar expression involving numeric
and string literals and/or constants in contexts where PHP previously
expected a static value, such as constant and property declarations
and default function arguments.
Yes, this is quite impossible, even you can not do like
function bar(){
return 'Hi';
}
class C {
const SENTENCE = bar();
//const SENTENCE = :SELF:foo();
public static foo(){
return "Hello';
}
}
echo C::SENTENCE;
#u_mulder is very correct.
You have missed reading the documentation correctly.
/**
* This example gets all ad groups in a campaign. To get campaigns, run
* GetCampaigns.php.
*/
Check this class instead.
here your campaign id is variable.
foreach ($page->getEntries() as $campaign) {
printf(
"Campaign with ID %d and name '%s' was found.\n",
$campaign->getId(),
$campaign->getName()
);
}

Answer 2

If you are using PHP 7+ then you can use this way .
// Works as of PHP 7
define('ALLVAR', array(
'dog',
'cat',
'bird'
));
echo ALLVAR[1]; // outputs "cat"
If you are using php < 7 Then use this way .
define ("ALLVAR", serialize (array ('dog','cat','bird')));
$my_const = unserialize(ALLVAR);
Inside your Class you can define a function for constants. Like below
class GetAdGroups{
public $options = array(
'app_id' => 'hello',
);
public function getConstant($key){
return $this->options[$key];
}
}
$a = new GetAdGroups();
print_r($a->getConstant('app_id'));