What's the Difference Between Extension and zend_extension in php.ini?
When I installed Xdebug through pecl, it added the following line to my php.ini file.
extension="xdebug.so"
and everything I used worked. Until today.
Today I was having trouble setting up Xdebug for interactive debugging. I couldn't get anything working until I changed the above to
zend_extension="/usr/local/lib/php/extensions/xdebug.so"
(Caveat: I think this is what got me working, but I'm not 100% sure)
This raised the question in my mind. What's the difference in loading an extension via extension= vs. zend_extension?
Answer
Zend_extentions are extensions that are built into the Zend engine itself. The engine parses, interprets and executes PHP script. Changing the engine changes the way that PHP works.
The included diagram will describe the main difference between an extension and a zend_extension.
Both types of extensions share lots of functionality. The difference between both types is mainly with the hooks that they register into the Engine. Despite it being very uncommon, an extension can be both a PHP extension and a Zend extension. Xdebug is a good example.
Find below image for main schema
