PHP
You can learn to develop an application in PHP in minutes. The hardest is to be able to write applications fast and to know the amount of time that will take you to do it. For this you need experience.
Once you know how to develop with pure PHP (using inner functions to connect to databases for example) you should focus on frameworks. You must not become a slave of a particular framework, you have to be able to work with all of them. (This should make you commercially viable for a development company, you should be Junior Developer at this stage)
Once you are able to crack most problems and debug legacy code in complex file structures -- like the ones found in Joomla! for example -- you can move on to Web services. With web services you can link plugins you developed for Wordpress (for example) to Twitter and Facebook. (This should help you push your carreer out of Junior into Professional or Advanced level.)
If you like to learn about accessibility and usability, this is the time. Empowered by all your knowledge and experience you can now make your applications more useful and interesting for more people. HTML5, CSS3 and W3 Standards can now be part of your portfolio too and you should by now be ready to become a Senior developer.
To be a Senior developer will demand that you are able to read and write technical documents. Each company will use a different notation but the basics is the same and UML is always useful. This is a must is you want to become a data systems analyst as well.
Frameworks
Methods
FPDF
Errors and error messages
