if only 与 only if 有什么区别?

问题描述:

if only 与 only if 有什么区别?
请各举例说明

If only 表示虚拟语气,如 If only I were you!如果我是你.If only (expressing a strong wish表示强烈的愿望)但愿,真希望,只要...就好了:If only he wouldn't eat so noisily.但愿他吃东西不这样大声就好了./If he ...