This post is part of the sub-series on Internationalizing a ClassicPress plugin which is part of the Internationalizing a ClassicPress plugin series.
A plugin can have a lot of strings to translate; the larger the plugin the more translations there are likely to be. It is quite common for developers to look for ways to reduce typing the same parameter every time through the use of variables or constants, but this must be resisted when it comes to setting the text domain parameter of the localization functions.
The reason for this is that it is not just the PHP of the plugin which needs to parse the translatable strings, but also the gettext libraries which are used to produce the POT templates, used by translators.
gettext is not a PHP parser, so it is unable to read variables or constants; it can only read the strings.
