Concatenate static properties in php

Question

I have two static properties I would like to access outside of a class, the second of which I would like to concatenate with the first.

Ex:

<?php
class Constants {
    public static $varToConcat = "bar";
    public static $concat = "foo " . self::$varToConcat;    // <-- How to concatenate?
}
echo Constants::$concat;
?>

The above gives the error:

PHP Fatal error: Constant expression contains invalid operations in ...../Constants.php on line 4

I've tried:

public static $concat = "foo " . $varToConcat;
public static $concat = "foo " . self::$varToConcat;
public static $concat = "foo " . $this->varToConcat;

How can this be done?

[Just use *actual* constants?](https://3v4l.org/4sG4l) Actually not exactly sure why this doesn't work with static properties' initializers, since it works with constants'. — Jeto, Feb 26 '20 at 19:34
@Jeto Paradigmatically, you are correct. These values will never change; I will use const. — voong, Feb 26 '20 at 23:18

Progrock · Answer 1 · 2020-02-26T19:37:40.633

0

If you want to concatenate outside the class do that:

<?php

class War
{
    public static $foo = 'Hello';
    public static $bar = 'World';
}

echo War::$foo. ' ' . War::$bar;

Output:

Hello World

edited Feb 26 '20 at 19:37

answered Feb 26 '20 at 19:30

Progrock

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score 0 · Answer 2 · answered Feb 26 '20 at 19:31

There's no way to do what you're talking about because static cannot be dynamic like that. What you could do is create a static method and get it

<?php
class Constants {
    public static $varToConcat = "bar";
    public static $concat = "foo ";

    public static function getConcat() {
        return self::$concat . self::$varToConcat;
    }
}
echo Constants::getConcat();

Concatenate static properties in php

2 Answers2