in chinese speak '生日快乐'

shēng rì kuài lè 生 日 快 乐

Generally，we often say生日快乐(sheng1 ri4 kuai4 le4) or 祝你生日快乐（zhu4 ni3 sheng1 ri4 kuai4 le4).When you say with elder people,you should say祝您生日快乐（zhu3 nin2 sheng1 ri4 kuai4 le4).If you say with some of your good friends,you also can say破蛋日快乐（po4 dan4 ri4 kuai4 le4）

"Happy birthday to you" You can say:祝你生日快乐（zhu ni sheng ri kuai le) or 哥们又老一岁（ge men you lao yi sui）

生 日 快 乐 -sang yat fai lok (in Cantonese) . Just in case you want to learn it. :)