I think the route to success with programming is much like maths, medicine or indeed any discipline, go for breadth first then depth. Don't spend all your time mastering one aspect, try to learn many different things at once even if you are actually only interested one specific thing. Once you have even just basic knowledge and familiarity with most facets of a field then you will be better equipped to approach any specialization.
So in your case its fine to learn PHP but I would encourage you to look at many different things that are unlike or even the antithesis of PHP. It will help you understand where general computing nomenclature comes from, what the limits of your chosen technology are, how best to implement it in a given environment and ultimately it will give you a much better understanding of the technology itself.
So in your case its fine to learn PHP but I would encourage you to look at many different things that are unlike or even the antithesis of PHP. It will help you understand where general computing nomenclature comes from, what the limits of your chosen technology are, how best to implement it in a given environment and ultimately it will give you a much better understanding of the technology itself.