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 the PHP environment, predefined PHP arrays containing variables, understanding and ability to write code to perform conditional operations, decision making, and looping concepts, among others. 

Key Competencies:

1. PHP Environment - Understanding of basic environment setup including web server, database, and installation and setting up PHP Parser. 
2. Variables - Basic understanding of PHP set of predefined arrays containing variables from the web server environment, including global and server variables. 
3. Decision-making and Loops in PHP - Basic understanding and ability to write code to perform conditional operations, decision making, and looping concepts in PHP.
4. Arrays and Strings - Ability to work with numeric, associative, and multi-dimensional arrays in PHP, and performing basic string operations such as concatenation, manipulation, and so on in PHP.