girl

Hi people. I need help. I want to use str_replace function a few times. THe problem is this: for example i have two words: "table" and "house".I want to replace one word's letters by other one, like: housetousetausetabsetable I have letters, when I click on "t", "house"-becomes "touse". But when after it I click "a", it bcomes "hause", not "tause", means it doesn't keep the previous change. I know I must keep that change somehow, but I don know how.Please reply if you know. Thanks