PHP

PHP is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. PHP stands for Hypertext Preprocessor, and is integrated with a number of popular databases, including MySQL, PostgreSQL, Oracle, Sybase, Informix, and Microsoft SQL Server. 

This key competency includes a basic understanding of PHP Regular Expressions, Forms, Error Handling, Built-in Functions, among others. 

Key Competencies:

1. Regular Expressions in PHP - Advanced understanding of the structure of a POSIX and PERL regular expression, brackets, quantifiers, predefined character ranges and performing operations using regular expressions.
2. Custom Error Handling -  Advanced understanding of the PHP provided framework to define custom error handling function, and working with PHP provided functions for debugging. 
3. Forms and Login - Ability to build dynamic websites with PHP Forms, with functionalities to store, update, retrieve, and delete the data in a database. Ability to use the PHP login script to provide authentication for custom web pages.
4. PHP Built-In Functions - Ability to seamlessly use and work with Built-In Functions ranging from arrays, collectables, class/object, forms, hash, network, pool, string, XML, and many others.