PHP7.4 (51 chars)
-
The function **$f** is inverting the last two chars of every word :
```php
$f=fn($s)=>preg_replace('#(.)(.) #',"2ドル1ドル ","$s ");
```
Usage :
```php
echo $f('Flippign Lettesr Aroudn');
```
PHP4 (51 chars)
-
The PHP4 [CLI](https://www.php.net/manual/en/features.commandline.php) equivalent is expecting *$argv[1]* to be a given string :
```php
echo preg_replace('#(.)(.) #',"2ドル1ドル ","$argv[1] ");
```