Certainly, PHP is a programming language. It is even Turing-complete language, which basically means that its "power" is equal to "power" of other programming languages. It is "real" both in strict (it really exists) and metaphorical sense (there are people making their living using PHP). So it seems that your teacher is somehow biased.
However, I see some point in your teacher attitude. PHP and Java come from radically different backgrounds. Despite being useful, PHP is very chaotic. Compare standard class library in Java with standard library of PHP functions - the latter looks just like huge set of unrelated tools. Moreover, there are a lot of PHP tutorials on the Web that are of, politely speaking, mediocre quality. Because you are learning how to program, it's best to learn using good tools, and Java is much better tool to learn programming than PHP.
PS. Google for "PHP sucks" to get tons of information why PHP isn't the best tool in the world.
