Seen this phrase written by a Chinese person:
[ài lǎohǔ yóu]
What does it mean? Failed to find it in dictionaries.
Is it some slang or 白话?
The meaning is: 我爱你.I love you. 爱(ài, love) sounds like the English "I"; 老虎(lǎohǔ, tiger) sounds like "love"; 油（yoú, oil) sounds like "you".
It originally comes from the movie 狮王争霸. In the movie 十三姨 teaches 黄飞鸿 (played by 李连杰 (Jet Li)) how to say I love you. 黄飞鸿 pronounces it as 爱老虎油. Afterwards 黄飞鸿's father overhears it and asks what it means. 黄飞鸿 says it means 问好 (to send one's regards, to say hello to). The father later in the movie also uses this phrase (but of course in the wrong meaning), ... .
After the movie came out, the sentence became quite popular and is often used online (for example on sites such as 微博 (weibo) and QQ).
Whether you could consider it as slang is depending on how you define slang (there is a lot of discussion about that). If you follow this definition of Slang by Bethany K. Dumas and Jonathan Lighter (wiki link)
I would say it has become slang (the 4 bullets are all fulfilled).
It is not a slang.
This is the way some Chinese learn to pronounce
because they can't speak English.