add php article

Author: connor11528

README.md

@@ -145,6 +145,8 @@ to potential employers. Score well on one of our public tests, and you will get
 
 ## PHP
 
+- **Efficient data structures for PHP 7** - https://medium.com/@rtheunissen/efficient-data-structures-for-php-7-9dda7af674cd - Medium article about implementing data structures with modern PHP
+
 - **30-seconds-of-php-code** - https://github.com/appzcoder/30-seconds-of-php-code - A curated collection of useful PHP snippets that you can understand in 30 seconds or less.
 
 - **SOLID Principles in PHP** - https://laracasts.com/series/solid-principles-in-php - SOLID represents a series of guidelines that developers can use to, if done well, simplify and clarify their code.