It depends if you have used any other programming language.
programming is all about logic really, the languages are all very similar, but mainly with syntax differences. A bit like going to different regions of the same country. The dialects may be different but the underlying language structure is the same.
It is difficult to say whether you can learn it without knowing your starting point.
One thing I will say though is how badly do you want to do it. If you think you can you are right, if you think you can not you are also right.
How much time have you got and how dedicated are you going to be?
Why do you need to learn it? Are you thinking of a career change or do you need something doing quickly?

My advice to you is why bother? Unless you have a burning technical desire to learn this, these are the things that over complicate life for marketers. There are thousands of programs pre-configured to use php, and thousands of programmers ready to implement your plan, so why bother? Do you like to use your ipad or must you know how all the circuitry makes it possible?

Having used Java, Python, C++, Ruby and Perl, using PHP seems almost very easy to pick up. There's no one quick way to learn. Find a problem and try to solve it with as much research as possible.

I call it learn-as-you-go - if that makes sense