Question

Can anyone tell me why this doesn’t work?
It’s just a crude example of what I’m trying to do somewhere else.

$stuff = array(
    'key' => __DIR__ . 'value'
);

However, this produces an error:

PHP Parse error:  syntax error, unexpected '.', expecting ')' in /var/www/.../testing.php on line 6

Also, this works:

$stuff = array(
    'key' => "{__DIR__} value"
);

Answer 1

The first piece of code does not work because it’s not a constant expression, as you are trying to concatenate two strings. Initial class members must be constant.

From the documentation:

[property] initialization must be a constant value–that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.