友誼永固的英文金句有：
1. Friendship is like a red thread. No matter where we go and what we do, it will never be lost.
2. A friend is always there when you need him.
3. A friend in need is a friend indeed.
4. Friendship is like a diamond, more valuable with age.
5. Friendship is like money, easy lost but hard to find.
6. True friendship lasts forever.
7. Friendship is like a river, always growing stronger with time.
8. Friendship is like a rock, solid and eternal.
9. A friend walks in when the rest walk out.
10. True friendship never grows old.
其中，一些經典的英文表達包括：“A friend is always there when you need him”（朋友總是在你需要的時候陪在你身邊），“True friendship lasts forever”（真正的友誼永恆不衰）。根據具體的語境和需求，您可以根據自己的喜好選擇適合自己的表達方式。