While I was on vacation in DC, my cousin, a Gastroenterologist heard me use this phrase and let out a small laugh. During one of her years in college, her English professor pulled her aside and explained to her the real phrase when she used it in a paper.
The phrase is a corruption of "for all intents and purposes" by persons who have heard the phrase, but have not read it in it's proper form. It means "for all intents, and for all purposes."
This phrase dates back to the 1500s and originated in English law, where it was "to all intents, constructions, and purposes." In modern usage, "for all intents and purposes" is also acceptable. The phrase means "for all practical purposes" and is generally used to compare two nonidentical acts or deeds, i.e., "She went to his room and drank with him, which she viewed to all intents and purposes as consent to sex." (In reality, only a sober 'yes' is consent to sex so to all intents and purposes she is a rapist). A shorter equivalent phrase is "in effect."
I guess that I didn't pay as much attention in English class as I had thought.