pspell_store_replacement() stores a replacement pair for a word, so that replacement can be returned by pspell_suggest() later. In order to be able to take advantage of this function, you have to use pspell_new_personal() to open the dictionary. In order to permanently save the replacement pair, you have to use pspell_config_personal() and pspell_config_repl() to set the path where to save your custom wordlists, and then use pspell_save_wordlist() for the changes to be written to disk. Please, note that this function will not work unless you have pspell .11.2 and aspell .32.5 or later.
Example 1. pspell_store_replacement()