This is a great idea - there's nothing wrong with neither PHP nor web development, but it's great idea to broaden your horizon.
First add another dynamic language to your tool-set: Perl or Python, preferably. This will be an easy transition and you will have a great degree of jobs open to you. There are dynamic language related jobs which aren't web-development: bioinformatics, data mining, toolsmith positions (build/release, qa, operations), platform engineering (creating custom OS images). Some of them may require domain specific knowledge for the more senior positions but would be willing to take on a strong coder on to a more junior position on the premises that you'd be able to pick up the knowledge and grow into a more senior role.
These positions will often either themselves involve projects in other languages (Java, C/C++) that you'd be able to pick up on the job or be in a larger engineering organization where you will be able to transition to these jobs.
And in all these cases your experience as a web developer will be appreciated and considered important.
I did the same transition myself: systems administration (involved in some internal web app development, lot of Perl scripting)-> undergrad (and becoming bored with systems administration after learning algorithms, operating systems, compilers, etc...) -> operations engineering (lot of tools development) -> Perl/C++/Java development. (At the mean time I've been working part-time on a Masters in Computer Engineering which is opening newer domain specific knowledge to me).
First add another dynamic language to your tool-set: Perl or Python, preferably. This will be an easy transition and you will have a great degree of jobs open to you. There are dynamic language related jobs which aren't web-development: bioinformatics, data mining, toolsmith positions (build/release, qa, operations), platform engineering (creating custom OS images). Some of them may require domain specific knowledge for the more senior positions but would be willing to take on a strong coder on to a more junior position on the premises that you'd be able to pick up the knowledge and grow into a more senior role.
These positions will often either themselves involve projects in other languages (Java, C/C++) that you'd be able to pick up on the job or be in a larger engineering organization where you will be able to transition to these jobs.
And in all these cases your experience as a web developer will be appreciated and considered important.
I did the same transition myself: systems administration (involved in some internal web app development, lot of Perl scripting)-> undergrad (and becoming bored with systems administration after learning algorithms, operating systems, compilers, etc...) -> operations engineering (lot of tools development) -> Perl/C++/Java development. (At the mean time I've been working part-time on a Masters in Computer Engineering which is opening newer domain specific knowledge to me).