Is it possible to evaluate constants inside double quotes? [duplicate]

Question

Is there a way to evaluate a constant inside double quotes to avoid concatenation using .?

For example, I can do things like:

echo "$variable";

echo "{$array["index"]}";

echo "{$this->myProperty}";

Unfortunally echo "{MY_CONSTANT}" don't work.

So, is there a way to evaluate a constant like in the examples above, avoiding concatenation?

I know is there alternatives to code and get the same result, but I'm aiming at just the constants.

My motivation to this is to write sql statements, for example:

$sql = "SELECT * FROM {MY_JOIN} WHERE id > 100";

Where MY_JOIN constant could be something like

"
orders
INNER JOIN
users
    ON (orders.user_id = users.id)
"

or to avoid something like

$dir = DIRECTORY_SEPARATOR."folder1".DIRECTORY_SEPARATOR."folder2".DIRECTORY_SEPARATOR;

I know I can write something like $separator = DIRECTORY_SEPARATOR and code $dir = "{$separator}folder1{$separator}folder2{$separator}"; but if it is possible, I would like to do this with the constants directly.

Answer 1

No, this is simply not possible.

However, two great workarounds for your particular examples:

sprintf('SELECT ... %s ...', MY_CONSTANT);

join(DIRECTORY_SEPARATOR, array('foo', 'bar', 'baz'));

Answer 2

Interesting, as the links suggested, we can do this with lambda functions, very interesting.

An working example:

<?php
$constant = function($cons){
   return constant($cons);
};

define('FOO', 'Hello World!');
echo "The string says {$constant('FOO')}";