Which programming language should i learn to build opencart type extensions

I know that i have to learn php , which other languages do i need to learn to start to make opencart type extensions .(magento, opencart, wordpress and other cms )

i am good at selling product online and i tired to partner with developers , so that they develop products and i sell them but it did pan out and know i am thinking why not learn myself how to code

for example http://ift.tt/1WjerMM

check example and tell me the language i need to learn