PHP Manual: Sets or gets the path for a domain

stringfalse bindtextdomain(string $domain, stringnull $directory = null)

The bindtextdomain function sets or gets the path for a domain.

domain: The domain.
directory: The directory path. An empty string means the current directory. If null, the currently set directory is returned.

The full pathname for the domain currently being set, or false on failure.

Version	Description
8.4.0	`directory` is optional now. Previously, the parameter always had to be specified.
8.0.3	`directory` is nullable now. Previously, it was not possible to retrieve the currently set directory.

Example #1 bindtextdomain example

<?php

$domain = 'myapp';
echo bindtextdomain($domain, '/usr/share/myapp/locale');

?>

The above example will output:

/usr/share/myapp/locale

Note:
The bindtextdomain information is maintained per process, not per thread.